Simulation study of a novel approach to couple compressed CO2 energy storage with compression heat storage in aquifers

Abstract

The integration of energy storage systems is essential for addressing the limitations of renewable energy generation, such as intermittency and fluctuations. This study introduces a porous media adiabatic compressed CO2 energy storage system (PM-ACCES) that combines thermal energy storage with compressed CO2 energy storage within aquifers at different depths. PM-ACCES aims to reduce the overall system complexity by eliminating the need for thermal storage systems at the ground level to store compression heat, while simultaneously integrating CO2 energy storage with sequestration. Through comprehensive numerical simulations and thermodynamic modelling, the study evaluates the performance of the PM-ACCES system under various operating conditions. The results show that, under the default conditions of this study, the average discharge power and charge power of the PM-ACCES with solar heating over 30 days are 4663.7 kW and 2342.9 kW, respectively, with a corresponding discharge capacity of 18,655 kWh and a charge capacity of 23,429 kWh. The PM-ACCES system can operate without external heat sources, achieving a discharge power of 3045.31 kW and a discharge capacity of 12,156 kWh, while attaining a higher round-trip efficiency of 51.93 %. Additionally, the study examined various factors affecting the energy storage performance of the solar-heated PM-ACCES. The findings suggest that improving wellbore thermal insulation and utilizing deeper aquifers can significantly enhance energy storage performance. However, increasing the circulation flow rate, while boosting charge and discharge power, reduces the round-trip efficiency. These findings provide a robust foundation for future optimization of CO2-based energy storage systems, offering a promising solution for integrating renewable energy into the power grid.