Dynamic behaviour of hydrogen fuel cells for automotive application

An experimental analysis was conducted on a 30 kW fuel cell power train with the aim to elucidate specific concerns of dynamic behaviour of hydrogen fuel cells in automotive applications. The study was conducted on a dynamic test bench able to simulate the behaviour of the reference vehicle, a minibus for historical centres collective service, on predefined driving cycle. The transient performance of the fuel cell system was firstly investigated without electric drive, using as load electric resistances electronically controlled. Experimental data were collected during warmup phases characterized by two acceleration slopes (150 W/s and 1500 W/s) and during a sequence of dynamic test cycles characterized by a very high acceleration slope of about 6 kW/s. The role of reactant feeding, humidification and cooling systems was investigated during all tests evaluating the performance during the transient steps in terms of cell voltage uniformity, expressed by the coefficient of variation C_v, used as statistical indicator. A driving cycle characterized by stop-and-go pattern and acceleration slopes compatible with a real utilization of the reference vehicle was finally adopted for tests on the overall power train. The results demonstrated a very good dynamic performance of the fuel cell stack as evidenced by the analysis of C_v, which resulted lower than 2.5% in all investigated working conditions, and by the overall power train efficiency which resulted about 30% with fuel cell system efficiency close to 50%.