Integration of energy storage systems based on transcritical CO2: Concept of CO2 based electrothermal energy and geological storage.

Energy storage systems are crucial for the massive deployment of renewable energy at a large scale. This paper presents a conceptual large-scale thermoelectrical energy storage system based on a transcritical CO 2 cycle. The concept is developed through the analysis of three high-efficiency systems: renewable energy storage using a thermoelectric energy storage system based on a reversible heat pump; a CO 2 storage system; and novel integration of energy storage using a reversible heat pump and geological injection of CO 2. The latter system efficiently integrates energy and CO 2 storage, taking advantage of the synergies between the operational requirements of both systems. The system uses CO 2 captured in stationary sources as a working fluid to store energy from renewables. The energy is stored and recovered in geological formation and heat/cold tanks, with energy storage based on sensible or latent heat of ice and water. A fraction of the CO 2 is expected to be permanently sequestered in the geological formation. The analysis of the time evolution of the system, under different operation profiles, shows the interest of the concept as a feasible integration for energy storage and CO 2 capture based on renewable energy, with an electric-to-electric efficiency varying between 40 and 50 %. • Reversible heat pump for electrothermal energy storage. • Transcritical CO 2 as working fluid and water for storage. • Inclusion of captured CO 2 and geological storage. • Round-trip efficiencies varying between 40 and 50 %. [ABSTRACT FROM AUTHOR]