Systematic Determination of Optimal Design-Points of Fully Integrated Power-to-SNG Process Chains Via Detailed Simulation of SOEC Stacks

Abstract

The denomination Power-to-SNG covers technologies for the production of synthetic natural gas (SNG) through methanation of electrolytic hydrogen and captured carbon, enabling long-term storage of electrical energy from intermittent renewable sources. A methodology leveraging the pinch method for the optimization of the operating conditions of power-to-SNG plants is presented and applied to a system layout comprising a series of fixed-bed methanation reactors, a biomass gasification process and solid oxide electrolysis cell (SOEC) stacks, which recover the heat produced by the exothermic methanation process. For the system optimization, a rapid SOEC stack model is built from an underlying detailed multi-physics 3D model whilst maintaining its accuracy. Simulations reveal a maximum system HHV efficiency of 85.2% while identifying optimal operating conditions for all plant components. Moreover, the necessity of integrated system optimization strategies is showcased, as the predicted ideal conditions in the system strongly differ from the optimal conditions of the isolated components.