Parametric Thermo-Economic Analysis of a Power-to-Gas Energy System with Renewable Input, High Temperature Co-Electrolysis and Methanation

A complete thermo-economic analysis on a cutting-edge Power-to-Gas system that comprises innovative technologies (a Solid Oxide Electrolyte Cell co-electrolyzer and an experimental methanator) and coupled with a renewable generator is provided in this study. The conducted economic analysis (which has never been applied to this typology of system) is aimed at the estimation of the synthetic natural gas cost of a product through a cash flow analysis. Various plant configurations—with different operating temperatures and pressure levels of the key components (electrolyzer: 600–850 °C; 1–8 bar)—are compared to identify possible thermal synergies. Parametric investigations are performed, to assess both the effect of the thermodynamic arrangements and of the economic boundary conditions. Results show that the combination of a system at ambient pressure and with a thermal synergy between the co-electrolyzer and the high-temperature methanator presents the best economic performance (up to 8% lower synthetic natural gas value). The production cost of the synthetic natural gas obtained by the Power-to-Gas solutions in study (up to 80% lower than the natural gas price) could become competitive in the natural gas market, if some techno-economic driving factors (proper size ratio of the storage system and the renewable generation, electrolytic cell cost developments and introduction of a carbon tax) are considered.