Low-Load Performance Analysis and Improvement Method of Automotive PEMFC System

Centrifugal compressors are widely used in automotive proton exchange membrane fuel cell (PEMFC) systems. Increasing the rotating speed of compressor could avoid surge under low-load conditions of PEMFC at the cost of reduced system net efficiency through increasing compressor power consumption accounting for more than 50% of the whole system. This paper proposes an Air-Bypass scheme to improve the efficiency of the PEMFC system under low-load conditions and employs a system model of a 60 kW PEMFC system with the GT-SUITE software. The influences of the Air-Bypass scheme on the operating point and power consumption of compressor, the oxygen excess ratio and the system net efficiency are analyzed. The results show that under the operation of ensuring a reasonable oxygen excess ratio under low-load conditions, the Air-Bypass scheme not only avoids compressor surge, but also reduces power consumption. In addition, Air-Bypass scheme makes the highest efficiency point of the PEMFC system reduced from 150 A to 50 A and the system efficiency of 20 A increased by 25%, which effectively improves the efficiency of PEMFC system under low-load conditions.