The Fabrication and System Optimization of Polymer Electrolyte Membrane Fuel Cell Stack

Abstract

The polymer electrolyte membrane fuel cell (PEMFC) is a promising energy conversion tech-nology for future sustainable development. The PEMFC has many advantages such as high power density, low operating temperatures, low emissions, silent operation, and fast start-up and shut-down. Furthermore, it has infinite possibilities for use in a wide and variety of applications from small scale mobile devices and robots to large scale cars and power plants. Many research groups in the world have been investigating about PEMFCs, but they have mainly focused on the single cell level or material properties. PEMFC Stack or system level studies are very important topics for fuel cell applications, because the performance of single cells and the performance of stacks are totally different. The stack consists of single cells but it is not as simple as stacking of single cells. In this study, to make a more effective stack, I tried to analyze the thermal distribution of the bi-polar plate of the stack in terms of three designs: (1) 100cm2 rectangular bi-polar plate, (2) 200cm2 square cell bi-polar plate, and (3) 200cm2 alternative square design bi-polar plate. I also employed four methods: (1) 100cm2 rectangular bi-polar plate without cooling, (2) 100cm2 rectan-gular bi-polar plate with water cooling, (3) 200cm2 square cell bi-polar plate with air cooling, and (4) 200cm2 alternative square design bi-polar plate with air cooling using COMSOL simulations. To optimize clamping pressure at the stack assembly, stack clamping pressure conditions were: (1) single cell 5000N axial load, (2) single cell 50 in lb bolt torque, (3) single cell 90 in lb bolt torque, (4) 16 cell stack 5000N axial load, and (5) 16 cell stack 90 in lb bolt torque. These pressure conditions have been analyzed by solid-works simulation and experimental load tests with pres-sure sensitive films. Furthermore, to find optimal stack operating conditions, I evaluated stack per-formance depends on gas and stack temperature: 40, 50, 60, and 70℃, relative humidity: dry, 60,80, and 100%, and pressure conditions: 0psi, 10psi, 20psi, and 30psi. In thermal distribution analysis, 100cm2 rectangular bi-polar plate with water cooling and 200cm2 alternative square design bi-polar plate with air cooling show well distributed simulation result. The temperature differences of two design are around 2℃ in the simulation. The clamping pressure simulation and experiments are present pressure distributions in every layer in the stack. The big-gest pressure was applied at end plate and gasket, bipolar plate, MEA, GDL in this order. The op-timal conditions of this stack from experiments are operation at 10psi pressure, 60% relative hu-midity of react gases, and 70℃ stack temperature. ⓒ 2013 DGIST