Computational Validation of Deep CO2 Closed-Loop Geothermal Systems (www.mdpi.com)

Researchers have developed a sophisticated modeling framework to enhance the performance of Closed-Loop Geothermal Systems (CLGSs) utilizing CO2 as a working fluid, as demonstrated in the D22 well of the Xiongan New Area, China. This three-domain thermo-hydraulic model incorporates dynamic CO2 properties, thermal resistance between wellbore and formation, and optimizes two configurations: U-tube and coaxial single-well systems. The study found that CO2 outperforms water, delivering an average thermal power of 186.3 kW with significantly lower wellbore heat loss, confirming the system's potential for efficient and sustainable geothermal energy extraction. The significance of this research lies in its comprehensive approach to addressing the long-term sustainability and operational efficiency of deep geothermal systems amidst environmental concerns. By validating predictions against field data, the study underscores the practicality of deploying CO2-based CLGSs in deep carbonate formations, indicating a mere 8°C temperature decline over 30 years of continuous operation. The findings also highlight operational constraints, such as optimal flow velocity and depth, which can guide future engineering applications in geothermal energy extraction, showcasing CO2's dual role in energy recovery and carbon sequestration.