Optimal year-round operation for methane production from CO2 and water using wind energy

In this paper, we present the optimal year-round production of synthetic methane from water electrolysis using wind energy, and CO2 from power plants. The plant consists of a wind farm, a system of electrolyzers which produces oxygen and hydrogen from water, a series of equipment used to purify and store the oxygen; and the purification of hydrogen using a deoxygenation reactor and its reaction with CO2 to produce synthetic methane. We operate the plant over a year, considering monthly variability in wind velocity for constant methane production, and for variable methane production. We formulate the problem as a multiperiod NLP. The investment of a plant devoted to synthetic natural gas production is 375 M€ for a production cost of synthetic methane of 13.1 €/MMBTU, a price that is currently over the selling price of natural gas. If the plant operates at constant methane production rate, the investment and production costs are almost double, but we can obtain credit from the electricity produced; 2.9 kg of CO2 per kg of CH4 produced can be reused by this process.