Evaporatively-Cooled PEM Fuel-Cell Stack and System

Abstract

In this paper we describe a new design and mode of operation for a PEM fuel cell. A fuel cell can be configured to operate with humidification of the membrane-electrode assembly (MEA) over the entire face of the cell, which minimizes local variations in relative humidity that can lead to mechanical stress on the membrane. Normally, using this humidification approach requires a rather large volume of circulating water to keep the stack in water balance and provide cooling to the cell by sensibly heating the circulating water. This external water volume can be a liability when attempting to start up a fuel cell power plant from the frozen state. By designing a system which allows the cell to be cooled evaporatively, the system water volume can be reduced significantly, and moving mechanical parts in contact with liquid water can be eliminated. We show a simple system schematic and some example results to demonstrate the viability of this novel system.