Publication: Descripción y modelado de una pila de combustible de membrana de intercambio protónico
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2009-10
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2009
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Abstract
La situación energética actual se basa en un modelo insostenible desde los puntos de vista económico y medioambiental. La tecnología de las pilas de combustible ofrece la posibilidad de disponer de energía de manera eficiente, limpia y abundante, ya que el hidrógeno que utilizan para funcionar se puede obtener de numerosas fuentes. Aunque existen numerosos tipos distintos de pilas, las de hidrógeno son las que ofrecen mejores características para su utilización en aplicaciones portátiles y de automoción. En este Proyecto de Fin de Carrera se han estudiado los fundamentos de funcionamiento de una Pila de Combustible de Membrana de Intercambio de Protones. Se trata de un sistema que consume hidrógeno y oxígeno para generar electricidad, calor y agua. Como sistema, consta de varias partes que funcionan de manera conjunta. Sin embargo, y debido a la extensión que supondría hacer un estudio de cada uno de esos subsistemas, este trabajo se centra en el estudio del apilamiento de celdas responsable de la generación de potencia como tal. Para ello se ha desarrollado un modelado utilizando el software Matlab/Simulink, utilizando las ecuaciones que rigen el comportamiento de las pilas de combustible. Mediante este modelado, se obtienen datos y gráficas fiables sobre el funcionamiento del sistema y su comportamiento ante variaciones de la corriente demandada por la carga, bajo diferentes condiciones de temperatura ambiental, temperatura de trabajo y presión de suministro de los gases reactantes. Para comprobar la verificación del modelado y sus posibles desviaciones, se han utilizado los datos técnicos y de comportamiento del Módulo Nexa de la compañía canadiense Ballard, que consiste en un sistema experimental basado en la tecnología de las pilas de combustible de hidrógeno Después de analizar los resultados obtenidos en el modelado, se puede concluir que las pilas de combustible de membrana de intercambio de protones funcionan a pleno rendimiento cuando trabajan a temperatura de servicio, ya que en estas condiciones la tensión de salida de celda es mayor que en las condiciones de arranque. Además, el aumento de presión de suministro de hidrógeno disminuye notablemente la resistividad de la membrana polimérica. Y sin embargo, a efectos resistivos, la variación en la presión de suministro de oxígeno apenas tiene influencia. Por otra parte, puede concluirse que la temperatura ambiental determina la humedad del sistema, ya que cuanto más caliente esté el aire circundante, más humedad contiene. _____________________________________________
The worldwide current energy status is based on an untenable model from the economical and environmental point of view. The fuel cell technology allows the use of an efficient, clean and full fitted energy supply because hydrogen, used as a fuel, can be obtained from many different sources. Although there are many kind of different fuel cells, hydrogen PEM fuel cells show a good performance when used for automotive or portable applications. This work studies hydrogen Proton Exchange Membrane Fuel Cells fundamentals. It is a system designed to consume hydrogen and oxygen to produce electricity, heat and water. As a system, it needs different subsystems to make the power generation possible. However, and due to the large volume of work, this document is focused on studying the main stack that is responsible for the electricity generation. To achieve this objective, a Matlab/Simulink software has been used for modelling the this power generation system, based on all those equations that controls the behaviour of the fuel cell. By this modelling it has been possible to obtain data and reliable graphics related to the system behaviour, after changing the current density under different conditions of ambient temperature, working temperature and gas supply pressures. It can be concluded that Proton Exchange Membrane Fuel Cells raise their top efficiency when working at the temperature they have been designed for, because under these condition the cell voltage at exit is bigger than voltage under start conditions. Plus, when increasing the pressure of hydrogen supply (Anode side), the internal resistance of the membrane decreases dramatically. However, changes of pressure on the oxygen supply (cathode side), has no important effects on the polymeric membrane or the power generation. It is also possible to conclude that ambient temperature decides the total humidity of the system. The hotter the ambient air is, the more humidity it absorbs.
The worldwide current energy status is based on an untenable model from the economical and environmental point of view. The fuel cell technology allows the use of an efficient, clean and full fitted energy supply because hydrogen, used as a fuel, can be obtained from many different sources. Although there are many kind of different fuel cells, hydrogen PEM fuel cells show a good performance when used for automotive or portable applications. This work studies hydrogen Proton Exchange Membrane Fuel Cells fundamentals. It is a system designed to consume hydrogen and oxygen to produce electricity, heat and water. As a system, it needs different subsystems to make the power generation possible. However, and due to the large volume of work, this document is focused on studying the main stack that is responsible for the electricity generation. To achieve this objective, a Matlab/Simulink software has been used for modelling the this power generation system, based on all those equations that controls the behaviour of the fuel cell. By this modelling it has been possible to obtain data and reliable graphics related to the system behaviour, after changing the current density under different conditions of ambient temperature, working temperature and gas supply pressures. It can be concluded that Proton Exchange Membrane Fuel Cells raise their top efficiency when working at the temperature they have been designed for, because under these condition the cell voltage at exit is bigger than voltage under start conditions. Plus, when increasing the pressure of hydrogen supply (Anode side), the internal resistance of the membrane decreases dramatically. However, changes of pressure on the oxygen supply (cathode side), has no important effects on the polymeric membrane or the power generation. It is also possible to conclude that ambient temperature decides the total humidity of the system. The hotter the ambient air is, the more humidity it absorbs.
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Pilas de combustible, Energía eléctrica