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Abstract:
The CEEGS (Carbon-Dioxide Electrothermal Energy and Geological Storage) project integrates electrothermal and geological systems to create a scalable energy storage solution using renewable energy. It combines transcritical CO2 cycles with underground storage, using captured CO2 for heat pumps to store surplus energy both thermally and mechanically. The system stores mechanical energy through pressure, similar to compressed air storage, and benefits from CO2 sequestration. Deep saline aquifers are identified as feasible geological reservoirs.
Initially, CO2 is injected continuously for two years (plume establishment stage) before entering charge-discharge cycles. The study focuses on the plume establishment and the impact of geochemistry on CO2. High-purity CO2 is required, but its composition can vary due to interactions with reservoir minerals and brine, affecting storage effectiveness. The study utilized PHREEQC and CMG-GEM for simulations, examining CO2 sequestration through dissolution and residual trapping.
Results showed that CO2 acidifies the reservoir, dissolving certain minerals. About 8.1% of injected CO2 was dissolved during the injection period. Impurities slightly increased the CO2 plume extent. Solubility and residual trapping were identified as dominant short-term sequestration mechanisms. Future research should extend the study period and explore different CO2 impurity levels to optimize system efficiency and costs.
