Thermodynamic Optimization of Proton Exchange Membrane Fuel Cell System S. O. Obayopo, T. Bello-Ochende and J. P. Meyer Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria 0002, South Africa Centre for Renewable and Sustainable Energy Studies Abstract: The proton exchange membrane (PEM) fuel cell is a promising candidate as zero- emission alternative power source for transport and stationary applications due to its high efficiency, low-temperature operation, high power density, quick-start up and system robustness. However, before this class of energy becomes competitive with traditional fossil fuel powered combustion engines, its performance and cost must be optimized. This study shows a three dimensional optimization study for a PEM fuel cell under different operating conditions and channel geometries. The continuity, momentum, energy and species conservation equations describing the flow and species transport of the gas mixture in the coupled gas channels and the electrodes were numerically solved using a computational fluid dynamics code. The effect of various operating parameters and channel geometries on the performance of the fuel cell was analysed. Results were validated by comparing the predicted results with experimental results published in the literature and were found to be in good agreement. The result obtained would lead to improvements in the design of fuel cells. Keywords: PEM fuel cells; optimization; parameters; geometry; performance _____________________________________________________________________ Introduction Fossil fuel usage has caused great environmental concern in recent years, such as the greenhouse effect and climate change. The increasing pollution in the environment due to these fossil sources has necessitated the search for other more efficient and cleaner alternatives for power generation. Fuel cell has been identified as a viable alternative for power generation purposes due to its efficiency and cleanliness. The fuel cell technology is environmentally friendly, requires low maintenance for the component parts and high theoretical efficiency due to direct conversion of energy. Fuel cell is being developed for a wide range of applications depending on the size and operating temperature. Proton exchange fuel cells (PEMFCs), using hydrogen is one emerging fuel cells with many advantages ranging from emission of water as waste, operation at low temperature for quick start-up, and uses solid polymer as electrolytes which reduces both construction and safety complications. This fuel cell type is highly being considered as an alternative power source for stationary and mobile applications. However, the large initial capital costs of fuel cell technology have offset the advantages it offers and slowed down its adoption for widespread applications (Rowe and Li, 2001; Siegel et al., 2003). Model development has paved ways for the development of this new energy system especially in the area of cost reduction. In addition, the expensive experimental procedures for studying the performance of fuel cells have greatly stimulated interest in efforts to develop models that could