Thermal Coupling Studies of a High Temperature Proton Exchange Membrane Fuel Cell Stack and a Metal Hydride Hydrogen Storage System

Abstract

High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) are promising candidates for simple and efficient stand-alone power generation systems. In spite of their relatively high efficiencies, especially at part load conditions, more than half of the chemical energy is converted into thermal energy during the electrochemical generation of electrical power. For stable and efficient operation, it is necessary to remove this heat efficiently and supply pre-heated reactants so as to minimize temperature variations within the cell. In the present study, we explore the possibility of using cathode air to act as coolant of the cell as well as the supplier of the heat required for hydrogen desorption from a sodium alanate-based hydrogen storage system. To this end, we use computational fluid dynamics to simulate the flow and heat transfer through a section of a 1 kWe HT-PEMFC stack and a thermally coupled hydrogen storage system. The calculations show that, with a cathode air flow rate seven times in excess of the stoichiometric requirement, it is possible to meet the triple requirement of supplying preheated cathode air; maintaining uniform stack temperature; and supplying the heat required for desorption of the required amount of H2.