CO₂‑based alternative fuel production to support development of CO₂ capture, utilization and storage

This proposed study compares CO₂‑based alternative fuel systems employing methanol, dimethyl ether and methane in the context of CO₂ capture, utilization and storage (CCUS) efforts. Chemical fuels offer an approach to store and transport renewable electricity over long spatial and time scales. Longer-term carbon capture and storage (CCS) system development can benefit from near-term carbon-based fuel production employing captured CO₂ as a precursor along with electrolytic hydrogen. Surplus renewable electricity (RE) or RE co-located with CCS developments can provide synthetic fuels to enable long-duration storage and long-distance RE transport. This study evaluates energy and exergy efficiencies when storing intermittent RE in the form of chemical fuels. The exergy analysis highlights the improvement potential in fuel synthesis, fuel combustion and other subsystems. The performance of the proposed carbon–neutral synthetic fuel systems are measured using H₂-to-fuel (chemical conversion efficiency), H₂-to-power and fuel-to-power efficiency metrics. Aspen Plus V11 is employed for the process simulation and Aspen Process Economic Analyzer V11 is used to compare the combustion economics. The results show that the methanol, DME and methane fuel systems provide H₂-to-fuel energy efficiencies of 88.4%, 85.2% and 83.3% and exergic efficiencies of 92.9%, 92.1% and 86.2% respectively; H₂-to-power energy efficiencies are 30.8%, 27.3% and 51.9% and exergy efficiencies are 30.5%, 27.1% and 51.7% respectively. These results highlight the relative merits of CCUS fuel pathways and potential for future efficiency improvements. The methane fuel pathway offers comparatively lower costs as compared with dimethyl ether and methanol routes. Furthermore, the detailed modeling efforts, efficiency results and sensitivity analyses conducted to investigate the performance of carbon–neutral synthetic fuel systems are presented and discussed.