Design and Applications of Low-Temperature Hydrogen-Fed Fuel Cell Stacks

Designing a low-temperature hydrogen fuel cell stack is a multidisciplinary activity. It involves knowledge of electrochemistry, mechanics, and thermodynamics. To explain the conceptual path that leads from a single cell to a complete power system, however, it is necessary to make a historical excursus and then show the essential information regarding thermodynamics, the components of a fuel cell stack system, and its applications. These are the keys to this article. The historical excursus helps understand how much time this technology needed and the steps necessary so far to reach today's level of maturity. A review of electrochemistry and thermodynamics is essential for understanding the design process. It starts with the choice of the stack architecture, which determines the characteristics and functions of the main components: electrochemical components (electrode and polymer electrolyte) and hardware components (bipolar plates, clamping plates, current collectors, and gaskets). Once the architecture is defined, it is possible to calculate the electrical parameters of the fuel cell stack (voltage and current), the active area of the single cell, the number of cells, and the cell voltage. However, this is not enough for an exhaustive discussion. It is necessary to illustrate the transition from the stack to the fuel cell system. Therefore the most significant components to support the operation of the stack (the “balance of plant”); and the applications of fuel cell systems in automotive, stationary, and portable contexts are the last and no less significant argument