Fuel synthesis with CO₂ captured from atmosphere: Thermodynamic analysis

Synthetic hydrocarbon fuel, derived from renewable energy and captured carbon dioxide from flue gas and/or ambient air, can close its carbon cycle and is an important approach to sustainable energy. In this study, the thermodynamic performance of a coelectrolysis process for producing hydrogen and carbon monoxide from water and captured CO₂ is investigated, based on current carbon capture and high-temperature electrolysis technologies. The exergy analysis is useful because it can reveal the energy losses due to irreversibilities and indicate possibilities for improvement of a process. Fuel synthesis systems integrated with or separated from different carbon capture technologies were evaluated and the analysis results have indicated that compared to the energy/exergy consumed by electrolysis, the energy/exergy penalty from CO₂ capture is insignificant. The thermodynamic efficiency of fuel synthesis could be increased by developing fuel generation technologies with lower electricity requirements, especially when using solar and nuclear energy.