Impact of water content on reversible Solid Oxide Cells: Semi-empirical modelling and effective electrolyte conductivity estimation

Solid Oxide Cell (SOC) performance strongly depends on temperature, pressure, gas composition, and flow rate. While extensive research has focused on SOC optimisation, the impact of water content on predictive reliability remains underexplored. This study investigates how fuel-side water concentration affects reversible SOC (rSOC) performance. Effective conductivity parameters were estimated from Electrochemical Impedance Spectroscopy (EIS) and polarisation curves under different fuel compositions, showing dependence on steam content due to transport and interfacial effects. These parameters were used to calibrate a semi-empirical rSOC model. For EIS-based conductivity estimation, increasing steam content reduced predictive reliability, defined as agreement between simulated and experimental curves. In SOEC mode, Root Mean Square Error (RMSE) increased from 0.0075 V at 50% steam to 0.072 V at 90% steam, while in SOFC mode from 0.038 V at 10% steam to 0.063 V at 50% steam. These results highlight the need to account for water-content effects in rSOC modelling.