Analysis of an intermediate-temperature proton-conducting sofc hybrid system

The performance of an intermediate-temperature (IT) proton-conducting solid oxide fuel cell (pSOFC) hybrid system is investigated in this work. The hybrid system consists of a 25-kW pSOFC, a micro gas turbine (MGT), and heat exchangers. Heat exchangers are used to recover the waste heat from SOFC and GT. The performance of the systems are simulated by using Matlab/Simulink/Thermolib. Flow rates of air and hydrogen are controlled by assigning different stoichiometric ratio (St). St considered in this study is 2~4 for air, and 1.3~1.5 for hydrogen. The operating temperature range is 500°C~700°C. Results show that the combined system efficiency increases as the fuel St decreases or air St increases. This is because lower fuel St means fewer fuel would be wasted from the fuel cell stack, so the combined system efficiency increases. On the other hand, as air St increases, the amount of recovered waste heat increases, and so does the combined system efficiency. The dynamic characteristic of the system is also simulated, and results show that air St does not have great influence on the startup time.