Design and strategies for operating PEM fuel cells with dry feeds

The operation of polymer electrolyte membrane fuel cells (PEMFC) with dry feeds was studied with different fuel cell flow channel designs as functions of pressure, temperature, and flow rate. Auto-humidified (or self humidifying) PEMFC operation was improved at higher pressures and low gas velocities so axial dispersion enhanced back-mixing of the product water with the dry feed. Autohumidified operation of the channel-less, self-draining fuel cell, based on a stirred tank reactor was demonstrated. Data were presented showing auto-humidified operation from 25° to 115°C at 1 and 3 atm. The auto-humidified self-draining fuel cell outperformed a fully humidified serpentine flow channel fuel cell at high current densities. Fuel cells designed with serpentine flow channels were not able to operate with dry feeds above 50°-60°C. The new design offers substantial benefits for simplicity of operation and control including: the ability to self drain reducing flooding, the ability to uniformly disperse water removing current gradients and the ability to operate on dry feeds eliminating the need for humidifiers. This is an abstract of a paper presented at the AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).