Technological and Engineering design of a megawatt proton exchange membrane fuel cell system

Abstract

For the large-scale application of Proton Exchange Membrane Fuel Cell (PEMFC) in the generation, multi-stack PEMFCs are usually adopted to meet high-power needs. The connection method among stacks, layout parameters, and operating parameters can greatly influence the performance and uniformity of system. A megawatt (MW) class PEMFC system with 20 stacks is proposed and modeled with a flow network model, a thermal model, and a PEMFC model. The temperature and voltage uniformity index (TUF and VUF) are defined to evaluate the system uniformity among stacks. The effect of several operating parameters, such as current density and hydrogen inlet pressure, and layout parameters such as spacing distance and the diameter of the pipe, on the stack voltage, system electricity efficiency, VUF and TUF are quantitatively compared. The results show that as the current density increases, the consistency of the system output decreases. The stack with the shortest gas transmission distance shows the best performance and the frictional loss is the main factor influencing the pressure differences among the inlet pressure of stacks. Under the inlet pressure of 2.5 atm, the voltage difference among stacks is within 0.15 V. From the perspective of overall cost and system output, a pipe diameter of 25 mm is more suitable for the design of the intake pipe in this system.