Performance investigation of fuel cell/battery and fuel cell/supercapacitor hybrid sources for electric vehicle applications

Abstract

This paper presents the utilization of a PEM fuel cell as a main power source in a distributed generation system, particularly for future electric vehicle applications. One of the main weak points of the fuel cell is its time constants dominated by temperature and fuel delivery system (pumps, valves, and in some cases, a hydrogen reformer). As a result, fast load demand will cause a high voltage drop in a short time, recognized as a fuel starvation phenomenon. Therefore, to employ a PEM fuel cell in dynamic applications, the electrical system must have at least an auxiliary power source to improve system performance when electrical loads at a dc bus demand high energy in a short time. The possibilities to use a supercapacitor or battery bank as an auxiliary source with a fuel cell main source is presented in detail. The very fast power response and high specific power of a supercapacitor or high specific energy of battery can complement the slower power output of the main source to produce the compatibility and performance characteristics needed in a load. The studies of two hybrid power systems for vehicle applications: a fuel cell/battery and a fuel cell/ supercapacitor hybrid power sources are explained. Experimental results in laboratory authenticate that energy storage devices can assist the fuel cell to meet the vehicle power demand and help achieve a better performance.