The value of CO2-Bulk energy storage with wind in transmission-constrained electric power systems

Highlights: • Investigated the value of CO₂-BES with wind in a transmission constrained system. • Developed an improved method for simulating CO₂-BES operation. • CO₂-BES can have a round-trip efficiency >100%. • CO₂-BES can increase revenue and utilization of transmission capacity. High-voltage direct current (HVDC) transmission infrastructure can transmit electricity from regions with high-quality variable wind and solar resources to those with high electricity demand. In these situations, bulk energy storage (BES) could beneficially increase the utilization of HVDC transmission capacity. Here, we investigate that benefit for an emerging BES approach that uses geologically stored CO₂ and sedimentary basin geothermal resources to time-shift variable electricity production. For a realistic case study of a 1 GW wind farm in Eastern Wyoming selling electricity to Los Angeles, California (U.S.A.), our results suggest that a generic CO₂-BES design can increase the utilization of the HVDC transmission capacity, thereby increasing total revenue across combinations of electricity prices, wind conditions, and geothermal heat depletion. The CO₂-BES facility could extract geothermal heat, dispatch geothermally generated electricity, and time-shift wind-generated electricity. With CO₂-BES, total revenue always increases and the optimal HVDC transmission capacity increases in some combinations. To be profitable, the facility needs a modest $7.78/tCO₂ to $10.20/tCO₂, because its cost exceeds the increase in revenue. This last result highlights the need for further research to understand how to design a CO₂-BES facility that is tailored to the geologic setting and its intended role in the energy system.