Experimental PEM-Fuel Cell Range Extender System Operation and Parameter Influence Analysis 2019-01-0378
Fuel cells as alternative propulsion systems in vehicles can achieve higher driving ranges and shorter refueling times compared to pure battery-electric vehicles, while maintaining the local zero-emission status. However, to take advantage of pure battery electric travel, an externally rechargeable battery can be combined with a fuel cell range extender. As part of a project funded by the Austrian Research Promotion Agency (FFG), an efficient air supply system for a fuel cell range extender is being developed. To this end, a 25 kW PEM fuel cell system test bench was set up at the Institute for Powertrains and Automotive Technology (IFA) of the Vienna University of Technology. The different parameter influences of the test bench, in particular of the air supply system, were analyzed and evaluated in terms of stack/system efficiency and functionality. The control software of the test bench was specifically developed for the flexible operating parameter variation. All adjustable variables of the system (air ratio, stack temperature, pressure, etc.) were varied and evaluated at steady-state operating points. Likewise, the system was analyzed during dynamic operation and fault cases in adverse operating conditions (water condensation, oxygen deficiency) were identified. The system's warm-up process has also been evaluated in regard to efficiency and functionality, since at lower temperatures, a larger air mass flow is needed to counteract water condensation inside the stack. Finally, the hydrogen purging losses were quantified at different operating pressures and purge intervals. It has been shown that above all, the air supply has a significant influence on the efficiency of the system and is decisive for the proper operation and further improvement of the system. In summary, it can be stated that, depending on the load point and operating conditions, a system efficiency between 42% and 56% is achieved. To that effect, a fuel cell range extender system, which still leaves some room for further system efficiency improvements regarding the air supply system, offers an attractive solution for a zero emission and comparably unconstrained driving range propulsion system for the future.
Johannes Höflinger, Peter Hofmann, Bernhard Geringer