The Value of CO2-Bulk Energy Storage to Reducing CO2 Emissions

Abstract

Carbon-dioxide (CO2) bulk energy storage (CO2-BES) is an emerging CO2 capture, utilization, and storage (CCUS) approach that stores CO2 that is captured from large point sources (e.g., fossil-fuel power plants) to time-shift electricity generated from variable renewable energy technologies so that it matches demand. Excess electricity can be used to compress and inject CO2 into sedimentary-basin geothermal resources, which stores the excess electricity as pressure and directly reduces CO2 emissions. The stored energy can be produced and used when electricity demand exceeds supply. CO2-BES indirectly reduces CO2 emissions if this time-shifting displaces electricity that would otherwise be produced by power plants that emit CO2. As a result, CO2-BES can have direct and indirect value to reducing CO2 emissions. In this study we applied a linear optimization program that we developed to determine the indirect and direct value that CO2-BES could have to reducing CO2 emissions over a day, and used the Electricity Reliability Council of Texas (ERCOT) electricity system as a case study. Using a CO2 price of $13/tCO2, we found that CO2-BES has an indirect value of 1.98 tCO2/MWh and reduced CO2 emissions through two mechanisms: (1) enabling a greater utilization of electricity generated by wind energy technologies, and (2) enabling natural gas power plants to displace electricity generated by coal-fired power plants. CO2-BES did not have a direct value to reducing CO2 in this study because a CO2 price of $13/tCO2 is less than the ∼$50/tCO2 to ∼$70/t CO2 cost of directly capturing CO2 from fossil-fueled power plants.