Flowsheet-based model and exergy analysis of solid oxide electrolysis cells for clean hydrogen production

Abstract

A solid oxide electrolysis cell (SOEC) is an electrochemical technology used for hydrogen production via a steam electrolysis reaction. Because the existing SOEC models are complicated, the aim of this study is to develop a user-friendly SOEC model in a flowsheet simulator (Aspen Plus). The developed model is used to perform a parametric analysis to investigate the effects of key process parameters, i.e., operating temperature, current density, steam concentration, sweep gas type and number of cells, on the SOEC performance. The simulation results show that the voltage and the overall overpotential decrease as the cell temperature increases, whereas the opposite trends are observed when the current density increases. From the energy and exergy analyses, the total energy demand slightly increases with cell temperature, whereas the electrical energy demand decreases. Based on an operating temperature of 1273 K when the SOEC uses oxygen as the sweep gas, the highest energy and exergetic efficiencies of 78.45% and 92.20% are achieved at a current density of 2500 A m−2 and at a steam concentration of 90% in a 500-cell stack.