Synthetic natural gas via integrated high-temperature electrolysis and methanation: Part II—Economic analysis

•Economic feasibility for electricity prices up to ∼67 $/MWh in “target” scenario.•Great impact of electrolysis section and heat exchangers network on capital cost.•Co-electrolysis system shows higher capital cost but lower sensitivity to electricity price.

This part II work is built on the energy performance results of part I and focuses on the cost of producing synthetic natural gas and sensitivity scenarios around main economic variables.Capital costs for each plant section have been evaluated taking into account operational parameters such as pressure and temperature of the SOEC. The costing and financial methodology is based on a discounted cash flow analysis that was used to calculate the specific cost of synthetic natural gas (SNG) which ensures economic profitability of the investment.The co-electrolysis case has higher capital, operating and maintenance costs; however it shows a weaker dependence on the electricity cost due to its higher plant efficiency. The impact of key parameters such as electrolysis stack cost, cell degradation rate and carbon dioxide feedstock cost were further investigated. Both “state-of-the-art” and “target” scenarios were defined to account for the expected enhanced technological maturity of the SOEC technology that is expected to occur in the following decade.For the co-electrolysis case, break-even electricity prices (i.e., costs that yield an SNG cost comparable to that of fossil natural gas) of 8 $/MWh and 67 $/MWh were calculated for “state-of-the-art” and “target” scenarios, respectively.