Simulation study of a novel methanol production process based on an off-grid Wind/Solar/Oxy-fuel power generation system

•The cost of carbon dioxide capture and storage is significantly reduced.•The output product of the system is methanol only.•Renewable energy utilization reaches 97.62 %.•The carbon emission is negative, about −0.344 kg carbon dioxide /kg methanol.•The levelized cost of methanol is 1.34 $/kg. Power-to-methanol technology represents a promising energy storage solution to manage the fluctuating supply and demand of renewable energy effectively. A novel methanol production process based on an off-grid wind/solar/Oxy-fuel power plant is presented in the paper, which consists of solar-wind energy, oxy-fuel combined cycle, proton exchange membrane electrolyzer, and carbon dioxide hydrogenation to methanol unit. The hydrogen produced by the proton exchange membrane electrolyzer is used to synthesize methanol, and the by-product oxygen is used in the oxy-fuel combined cycle. At the same time, low-cost carbon capture is achieved with liquefied natural gas cold energy utilization, and the collected carbon dioxide is used to synthesize methanol. The system carbon emission is negative, about −0.344 kg carbon dioxide/kg methanol, the system has no other products except methanol. The structure of renewable energy has a significant impact on the technical and economic performance of the system. Therefore, a comparative analysis of different wind/photovoltaic installed capacity ratios is carried out. The case study shows that the proposed system has the best performance when the wind/photovoltaic installed capacity ratio is 25 %/75 %, with a renewable energy utilization of 97.62 %, methanol production cost of 1.34 $/kg methanol, and an energy efficiency of 63.5 %. The proposed system may be a practical solution for methanol production from renewable energy.