Optimization of the hydrogen utilization of PEM fuel cell systems: test bench concept and research scope

Abstract

With the rising technology readiness of PEM fuel cells, they are a promising alternative power source for realizing zero-emission aviation. However, the large amount of green hydrogen required for future aviation underlines the urgency to develop efficient operation strategies to maximize the utilization of hydrogen in fuel cell systems. For this purpose, a fuel cell test bench, consisting of an externally humidified, pressurized and water-cooled PEM fuel cell in the 150 kW power range, was designed. It also includes the recirculation and cyclic purge of the anode gas. The aim is to utilize the test bench for determining the energy- and mass transport of the fuel cell system. This is realized by measuring the humidity, temperature and pressure at all in- and outlets of the balance of plant components at the cathode side. In the anode system the mass flow, the hydrogen and water concentration at the fuel cell in- and outlet and the pressure and temperature before and after the recirculation pump are measured. The procedural instrumentation of the test bench is completed by the pressure and temperature sensors upstream and downstream of the fuel cell, and by the mass flow meter at the coolant side. In terms of electrical instrumentation, the stack and single cell voltage as well as the current are measured. The test campaign is scheduled in two phases. In phase one, the performance of the fuel cell system is optimized by varying the stack temperature, the cathode pressure, the cathode stoichiometry, the cathode humidity and the cell voltage using a statistical design of experiment approach. In the second phase, the maximization of hydrogen utilization as well as the investigation of the relation between anode gas mixture and fuel cell performance is investigated. Therefore, the design of experiment treatment factors of the second test phase are the anode purge duty cycle, the anode purge frequency, the recirculation pump speed, the cathode pressure, the pressure difference between anode and cathode as well as the cell voltage.