Cold Start Improvement of a Polymer Electrolyte Fuel Cell System by Oxygen Enrichment

Kurzfassung

The startup ability of a polymer electrolyte fuel cell System from subzero temperatures is essential, especially for transportation applications in winter scenarios. Extensive research has been carried out on fuel cell cold start for automotive applications with cathode air supply. In this study oxygen enriched cathode gas is used during fuel cell cold start. The aim of this experimental work is to study the influence of the cathode gas oxygen content on the cold start behaviour of a PEFC stack. Numerous tests with a 4 kW commercial fuel cell system were conducted starting from -10 °C to lower temperatures like -20 °C varying the oxygen content and other operational parameters, like the oxygen excess ratio or the starting voltage of the fuel cell stack. It was found that increasing the oxygen content shortens the cold start duration. As it can be seen in the figure this improvement is nonlinear. Increasing the content of O2 up to 30-35% can significantly reduce the startup time. The cold start processes as well as the optimal parameter combination at very low temperatures for following cathode gas: pure oxygen, synthetic air (20.9% O2) and synthetic oxygen-enriched air (optimal % O2 for the system) are to be presented. Finally, some fuel cell system concepts to improve the fuel cell cold start capability including oxygen enrichment will be discussed.