Thermocells represent a promising way to utilize heat as a power source. The aim of this work is to develop a thermocell with identical gas electrodes using molten carbonate-based electrolytes. The cell can generate power from waste heat, and can also utilize the CO2 rich off-gas available in metal producing industries. The flow rate of the gas supply to the electrodes needs to be optimized. Its effect on the Seebeck coefficient was not studied systematically before. The addition of solid oxide to the molten carbonate melt alters also the system's Seebeck coefficient. We report measurements where we vary the content of solid oxide in the liquid eutectic electrolyte mixture as well as the electrode gas flow rate. The Seebeck coefficient is reported for various ratios of eutectic (Li, Na)(2)CO3 molten carbonate and dispersed solid oxide MgO, and for varying gas (CO2|O-2) flow rates to the electrode interfaces. (C) The Author(s) 2017. Published by ECS. All rights reserved.