Numerical study on the performance of an inter-seasonal CO2 thermal storage system in anticlinal aquifer

CO2 has been identified as a promising working fluid for heat transfer in subsurface spaces. This study introduces a CO2 aquifer thermal energy storage (CATES) system, utilizing CO2 to store heat in aquifers, which achieves a combination of CO2 sequestration and utilization. CATES is a phase change thermal energy storage system that can extract the latent heat of liquefaction of COQ by cooling supercritical COQ at ground level to a temperature below its critical point. The flow and heat transfer characteristics of CO2 in inter-seasonal storage and the feasibility of CO2 as a working fluid in aquifer thermal storage are examined. A non-isothermal, multiphase flow numerical model integrating the wellbore and reservoir is developed to simulate CATES in anticlinal structural aquifers. The performance of the CATES system is systematically evaluated, examining factors such as aquifer permeability, depth, and heat storage temperature that might impact its thermal storage characteristics. The findings of the study indicate that CATES exhibits favourable thermal storage properties. Under the baseline scenario, it achieves a heat extraction power of 6526.03 kW, with an average heat recovery efficiency of 78.78% and an energy efficiency of 94.25%.