Evaluation of ceria electrolytes in solid oxide fuel cells electric power generation

Samaria-doped ceria solid oxide fuel cells (SOFC) single cells have demonstrated power densities >250 mW/cm(2) at 700 degrees C and stable performance for 15,000 h. Though encouraging, issues of stack performance and efficiency due to mixed conduction remain. Stacks operated on H-2/3% H2O show approximately half the power density expected from single cells. A coupled thermal-electrochemical model which included conduction heat transfer in the solid and convection to the reactant gases was developed. The model was used to predict stack efficiencies using ceria-based SOFCs in power plant applications. Analyses indicate that ceria SOFCs may provide as high as 42% electrical efficiency when operated on humidified hydrogen fuel. These efficiencies are surprisingly high and challenge the notion that mixed conductors are unsuitable for such applications. (C) 1999 The Electrochemical Society. S0013-4651(97)11-042-3. All rights reserved.