Analysis and Evaluation of a TCO2 Electrothermal Energy Storage System with Integration of CO2 Geological Storage

The goal to reduce greenhouse gas emissions necessitates the increase in RES utilization. To accomplish this goal, energy storage solutions are required. This study investigates the performance of an electrothermal energy storage system, the CEEGS, which consists of an above-surface energy storage system and a below-surface geological system. The focus is set initially on the analysis of the above-surface system to gain insight into its operation. Then, steady-state optimization is utilized to identify the operating conditions that maximize the system performance, before investigating the below-surface system integration and the effect that the geological conditions have on system performance. For the above-surface system, efficiency (ηR-T) up to 46.89% is calculated. For systems integrated with CO2 geological storage, two case studies are examined, presenting higher ηR-T compared to the above-surface system (Case study 1: 50.37%, Case study 2: 67.39%). The optimal ηR-T for Case study 2 is achieved for higher injection/production pressures and temperatures conditions and minimal ΔP and ΔT between injection and production. In conclusion, it is the selection of the geological storage conditions that contribute the most to the optimal ηR-T; thus, the selection of the appropriate geological storage formation is imperative.