El aumento de voltaje no es el único beneficio que se obtiene al trabajar a alta presión, del mismo modo las pérdidas de potencia no ocurren solamente por utilizar un compresor. En los sistemas donde se utiliza un reformador para el combustible, se obtiene una de las ganancias más importantes.
Otro factor a favor de la presurización se da cuando hay que humidificar los gases reactivos. La humidificación es mucho más fácil de hacer si el aire de entrada está caliente, porque hay mucha energía disponible para evaporar el agua. Una temperatura alta está siempre asociada con los gases comprimidos, en ellos se necesita menos agua para lograr la humidificación, y a temperaturas elevadas la diferencia es apreciable. Fundamentalmente es muy difícil lograr la humidificación en las PEMFC que funcionan a temperaturas por encima de los 80°C si no se presuriza el sistema a 2 o más bar [6].
En las PEMFC grandes, las trayectorias de los gases reactivos son bastante largas, por lo tanto se necesitará cierta presión para mantener el flujo de gas en las celdas.
En sistemas simples como la Figura 2.21, el compresor es generalmente del tipo tornillo, los cuales son bastante ruidosos, comparados con el resto del sistema. Esto genera un problema importante ya que disminuye una de las principales ventajas de las PEMFC con respecto a otros sistemas de generación.
2 1 P
Aumento de potencia C ln I n [Watts] P
§ ·
= ¨ ¸
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En la práctica la mayoría de los sistemas pequeños (<1 kW), funcionan a una presión cercana a la del ambiente, son los sistemas grandes los que habitualmente funcionan a presiones más altas [6].
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