Title

Studies on novel designs of proton exchange membrane (PEM) fuel cells

Date of Completion

January 2007

Keywords

Engineering, Mechanical

Degree

Ph.D.

Abstract

Proton exchange membrane (PEM) fuel cells are promising power generation sources capable of delivering high power density and being adaptable to different applications. However, widespread commercialization of PEM fuel cells is primarily challenged by their low reliability in service. This dissertation addresses two issues to improve the fuel cell reliability, one pertaining to mitigating the factors promoting membrane electrode assembly (MEA) degradation and failure, and the other aimed at reducing the system complexity. ^ During the operation of a PEM fuel cell, significant variation of the local current density could exist along the cell, causing sharp temperature and stress gradients in certain points, affecting the water management, and creating local hot spots and "pin-hole"s, all of which severely impact membrane reliability. The first goal of the dissertation is to minimize the local current density variation and potentially improving membrane reliability by determining the optimal operating parameters of PEM fuel cells with the objective of constraining the current density variation, which usually causes the local hot spots and degrades the membrane reliability. Computational studies are presented to determine the optimal operating conditions. ^ Toward reducing the system complexity, a second focus of the dissertation is to explore a new passive air-breathing fuel cell design, in which the air is drawn at the cathode surface by natural convection from the ambient, and arrays of air-breathing cell units could be designed to meet required power and voltage needs. By eliminating the balance of plant associated with the air feed at the cathode, the system complexity is reduced, contributing to improve the entire system reliability. Numerical studies are conducted to investigate the performance of a single as well as array of air-breathing fuel cell units. ^ Overall, the studies in this dissertation deliver new approaches and fundamental insights to addressing some of the current limitations in fuel cell technology. ^