Hydrogen is considered a clean energy carrier. At present, the production of hydrogen via a solid oxide electrolysis cell (SOEC) is of interest because steam is only used as a reactant. In addition, synthesis gas (syngas) production via the SOEC is a choice for decreasing carbon dioxide as steam and carbon dioxide are decomposed into hydrogen and carbon monoxide (syngas). However, the hydrogen and syngas production of SOEC have high operation cost due to high electrical energy consumption. In this work, a solid oxide fuel-assisted electrolysis cell (SOFEC) is studied. In the SOFEC operation, methane is added to the anode side of the SOEC and reformed to produce hydrogen. Hydrogen produced is used to produce electricity for use in the electrolysis process and thus, the energy demand of the SOEC can be reduced. An electrochemical model of the SOFEC is used to analyze the performance of the electrolyzer with/without the addition of methane. In addition, the effects of key operating parameters, such as current density, steam-to-carbon ratio, temperature, pressure and fuel utilization, on the electrolyzer cell performance is discussed. The simulation results show that the performance of the SOFEC is higher than the conventional SOEC as it requires a lower power input. Furthermore, it is possible to run the SOFEC without an external electrical energy input.

Thesis (M.Eng.)--Chulalongkorn University, 2014