A generic physical model for a thermally integrated high-temperature PEM fuel cell and sodium alanate tank system

Abstract

We study the thermal coupling potential between a Sodium Alanate tank and a High-Temperature PEM fuel cell using a heat transfer fluid to redirect a fraction of the thermal power produced during normal fuel cell operation towards the walls of the metal hydride tank in order to maintain hydrogen desorption. The remaining thermal power is then rejected to the environment by introducing an appropriately adjusted excess of air directly to the fuel cell cathode. Assuming a typical tubular geometry for both the metal hydride tank and the fuel cell, we propose a generic physical model that accounts for heat transfer in all the components of the integrated system (fuel cell, metal hydride tank and heating jacket), as well as H2 desorption kinetics and flow in the tank. Based on this model we study the dynamics of the coupled storage/usage system in terms of H2 pressure in the tank and temperatures in the tank and the fuel cell. Focus is primarily placed on the parameters that lead to steady-state operating conditions (i.e. the flow rate of air towards the fuel cell and the velocity of the heat transfer fluid in the heating jacket), with respect to the electrical power of the fuel cell.