Contribuciones a las pilas de combustible de electrolito polimérico (PEFC) de potencia media y refrigeradas por airefundamentación teórica del proceso de fabricación del stack y estudio experimental del balance de planta

Zusammenfassung

In recent years, the scarcity and dependence on fossil fuels has contributed to the promotion of renewable energies by public administrations, in addition to the concern for climate change and the harmful effects of polluting emissions. Therefore, there has been interest in developing renewable energy sources, including hydrogen fuel cells, which are capable of generating clean energy. Regarding the types of fuel cell technology, polymer electrolyte fuel cells (PEFC) are characterized by their wide variety of applications such as portable equipment, stationary applications or automotive, as well as systems for situations of emergency. To build a complete PE fuel cell, from the single cell to the stack is needed to assemble similar cells and the number of cells stacked varíes depending on the electrical power required. In a cell, there are two parts that receive special attention: the set that form the electrode and the membrane (MEA) and bipolar plates (BPs). Therefore, a detailed review of the manufacturing processes that are involved in these two parts will be carried out, describing the catalyst deposition techniques for the implementation of the MEA and the manufacturing methods of BPs ordered chronologically, and also includes how to assemble the cells to build a stack that can provide the required energy. In addition, another advantage of air-cooled polymer electrolyte fuel cells (AC-PEFC) is their ability to integrate the oxidation and cooling subsystems into just one. This feature reduces not only the weight, volume and cost of the fuel cell, but also the complexity of the control. The oxidant/cooling subsystem along with three others (fuel, electrical and control) make up the Balance of Plant (BoP), which together with the stack, comprise the fuel cell system. It is common to find works focused on analyzing the influence of the oxidant/cooling subsystem in a fuel cell. However, studies of the fuel subsystem (which is responsible for providing hydrogen for its oxidation-reduction reaction with oxygen to form water) are difficult to find in the scientific literature. It seems that the configuration of the fuel subsystem would have no influence on the overall performance of the system. But based on results, it shows how the performance of the fuel cell is conditioned by the configuration of the fuel subsystem. Therefore, an exhaustive study of an AC-PEFC type fuel cell is presented paying attention to the fuel supply subsystem giving the keys for the configuration of a more suitable BoP, which guarantees the best performance, with the BoP design more easy and the mínimum complexity. Subsequently, an experimental study of the configuration of the oxidant/cooling subsystem of an AC-PEFC is presented. According to the scientific literature, the studies carried out have always been more focused on the study of the rest of subsystems, instead of focusing on the oxidant/cooling subsystem, although an adequate design and size of the subsystem are fundamental for the proper functioning of the stack. The analysis that is carried out attempts to solve sorne problems that may appear if the design of the oxidant/ cooling subsystem has not been optimized adequately. These problems are related to important aspects, since they would influence the performance, the efficiency of the complete system and the distribution of the temperature on the stack