Developing Standard Operating Procedures for Solid Oxide Fuel Cell Testing at Elevated Pressures

Turbine-fuel cell hybrids in which high temperature fuel solid oxide fuel cells (SOFCs) are placed within the hot section of the engine are being studied as compact and efficient sources of electric power for aircraft with distributed electric propulsion. However, there are few studies that consider the effect of pressurization on fuel cell performance making it hard to make accurate predictions of such system’s performance. One reason for this lack of data is that measuring SOFC performance at pressure is difficult: the cell must be tested in a pressurized furnace at temperatures up to 750C while remaining electrically isolated from its surroundings. This is made harder by the relatively large number of fluidic and electrical connections and components required to control temperature and pressure, deliver reactants to and from the cell in the correct proportions, collect the cell’s current, measure its voltage, and measure pressures, temperatures, and mass flow rates in various other places in the system. This paper describes the development of a set of standard operating procedures for the University of Maryland’s pressurized SOFC testing facility. Such procedures are essential for ensuring that the facility operates safely while producing reliable data. The current version of the SOP in use highlights the additional complexities that come with testing SOFCs at elevated pressures. The use of a pressure vessel inherently limits access to the cell, sensors, and balance of plant equipment. As such, the SOP contains continuity and leak checks at multiple stages of the build-up and sealing process to ensure problems can be resolved with as few obstructions as possible, saving time and potentially materials in the process. Assuming the sealing process is completed with no issues, pressurized testing increases the potential for leaks outside the pressure vessel, while the varying pressure conditions inside can lead to transient pressure differences between anode, cathode, and bath flows. Therefore, it is important to include more precautions to reduce the likelihood of gas leaks than for atmospheric fuel cell testing, and set procedures for changing the pressure setting must be established to avoid damage to the SOFC under test.