Multivariate dynamic response characteristics of solid oxide fuel cells under continuous variable load scenarios

Solid oxide fuel cells (SOFCs) is an ideal candidate for power generation due to its flexible fuel options, clean operation process and high electrical efficiency. To further clarify the performance of SOFCs under continuous variable load scenarios in distributed energy systems, a dynamic model accounting for mass, heat and charge transfer processes is established and validated in this study. Four distinct continuous load variation patterns and a set of opposing step load changes are applied to the SOFC to systematically investigate the dynamic response characteristics and off-design performance over a wide operating range. The results reveal that mismatched electrochemical reaction rate and gas transport rate lead to inevitable fluctuations in the voltage and power responses of the SOFC. The influence of the gas transport lag becomes more pronounced as the duration of current variation shortens or the rate of current variation increases. The dynamic response of the SOFC is strongly governed by the current variation rate. Thress distinct voltage response characteristics are obtained under variable load conditions. As fuel utilization increases, a temporary voltage increase is observed in sequence across the exponential, accelerated and linear rise current scenarios. With increasing current, the influence of the air flow rate exceeds that of the fuel flow rate.