Modeling, optimization and comparative assessment of power-to-methane and carbon capture technologies for renewable fuel production

Power-to-X systems which convert electrical energy into stable chemical energy carriers are a promising solution to the long-term energy storage challenge posed by the increasing market penetration of intermittent renewable power sources. In this paper, a systematic and flexible method for optimizing the steady-state operating conditions of Power-to-Methane (PtM) plant concepts is showcased and applied to perform a comparative assessment of a multitude of PtM process chains. As opposed to existing studies, a large number of comprehensive PtM system models integrating multiple carbon capture technologies and Solid Oxide Electrolysis Cell (SOEC) stacks are optimized. Using detailed 3D SOEC stack simulations and interpolation-based model reduction, the performance of electrolyte-supported (ESC) and cathode-supported cells (CSC) integrated in a variety of PtM systems with air and pure oxygen sweep gas concepts is compared. A total of 20 plant concepts using different combinations of carbon capture (biomass gasification, amine gas treatment, direct air capture) and methanation (fixed-bed, slurry bubble column) technologies are investigated using the pinch method. ... mehrThe results demonstrate that thermal integration of the carbon capture process in PtM systems can raise the total efficiency of the process chains by up to 10.9% for direct air capture and 10.4% for amine gas treatment, with the plants reaching high heating value efficiencies of 70.2% and 84.6% respectively. Endothermic, high temperature operation of SOECs is shown to consistently yield the highest PtM efficiencies due to the minimization of cell overpotentials and power inverter losses. Conversely, exothermic operation of SOECs thermally integrated with energy-intensive carbon capture processes is shown to significantly lower capital expenditures (CAPEX) while incurring an efficiency loss lower than 1% compared to thermoneutral operation.