Integration of wind, solar and biomass over a year for the constant production of CH4 from CO2 and water

•CO2 can be useful as carbon source to produce fuels.•Synthetic methane is produced using CO2 and renewable hydrogen.•The solution suggests power production from Biomass, but for in Summer, and the production of hydrogen from electrolysis.•The framework computes the limits for the selection of the energy source.

In this paper we optimize the combination of biomass, wind and solar energy for the constant production of synthetic methane. Biomass is used for the production of power and/or hydrogen. Photovoltaic solar and wind energy are used to obtain power. Water is electrolyzed generating oxygen and hydrogen, which is used to synthesize methane with CO2. The model is formulated as an MINLP. The optimization suggests the production of power using solar energy complemented with biomass. Biomass is processed using indirect gasification and steam reforming. The hydrogen is produced from water electrolysis. The investment and production costs are 175 M€ and 0.38 €/Nm3 respectively. A sensitivity analysis shows that biomass is preferred for prices and investment below 50 €/t and 1500 €/kW. Solar energy is used for high cost of biomass if solar incidence is above 1200 kWh/m2 yr. Wind use is restricted to low solar incidence and wind velocities above 9 m/s.