Techno-economic assessment of a negative-emission energy storage concept: compressed oxygen energy storage with oxy-fuel biogas combustion

Energy storage is essential for balancing power systems with high shares of intermittent renewables, yet conventional compressed air energy storage systems rely on fossil fuels during discharge and thus retain a carbon footprint. This study addresses the challenge of developing a dispatchable storage system that simultaneously provides grid balancing and permanent carbon removal. Integrating oxy-fuel biogas combustion and carbon capture and storage into a compressed oxygen energy storage configuration can enable electricity dispatch while achieving net-negative emissions. A thermodynamic process model was developed to simulate the integrated charging-discharging cycle. The designed system operates with charging and discharging capacities of 11 and 25 MW, respectively, purchasing 22.9 MWh during a 2-hour charging period and delivering 100.6 MWh during a 4-hour discharge, while capturing 72.3 tCO 2 per cycle; the round-trip efficiency is 40.3%. Under assumed biogas and electricity prices of 36 and 20 $/MWh, the minimum selling price of electricity is estimated to be 163.4 $/MWh during discharge, which decreases by 77% if a 100 $/t subsidy for biogenic CO 2 capture is applied. Results suggest that the proposed concept could serve as a dispatchable energy storage technology that simultaneously enables permanent removal of biogenic CO 2 .