Extreme management strategy and thermodynamic analysis of high temperature H2O/CO2 co-electrolysis for energy conversion

H2O/CO2 co-electrolysis through solid oxide electrolysis cell (SOEC) combined with renewable energy system and Fischer-Tropsch system to produce fuels is a promising way to convert electrical energy into chemical energy. In this work, fuel composition, conversions of H2O and CO2, selectivity to H2, CO and CH4, and yields of H2, CO and CH4 for H2O/CO2 co-electrolysis are investigated based on the thermodynamic equilibrium under the boundary condition without carbon deposition. High selectivity to CH4 can be reached at suitable MH2O/MCO2 ratio and low temperature, while high selectivity to CO and H2 can be reached at high temperature according to the thermodynamic equilibrium results. When the operating temperature of SOEC is low, the conversions of H2O and CO2 cannot reach high due to carbon deposition, which can be improved by increasing MH2O/MCO2 ratio. When the operating temperature of SOEC is high, the conversions of H2O and CO2 can reach high without carbon deposition, which can be higher than 90% at 1073 K according to the thermodynamic equilibrium results. The syngas with different H2/CO ratios for Fischer-Tropsch synthesis of different fuels can be produced by selecting appropriate co-electrolysis condition.