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Techno-Economic Analysis of CO2-Stimulated Geothermal Systems
Thomas MAYER, Guoxiang LIU, Scott BEAUTZ, Luciane CUNHA, Huihui YANG, Jay CHEN, Jacqueline Alexandra HAKALA, Kelly ROSE, John ROGERS
[National Nuclear Security Administration MSIIP, USA]
In recent years Enhanced Geothermal Systems (EGS) have shown increasing viability for meeting the demand of scalable renewable energy. EGS’s have the unique advantage of geographic flexibility while also having massive energy potential, which has the possibility of being much higher than traditional geothermal systems. However, EGS faces challenges, majorly high initial capital expenditures and uncertain economic returns. This study investigates techno-economic feasibilities of EGS. In which we aim to both contribute to a deeper understanding of CO₂-based geothermal enhancement against water-based baseline and support the development and operation in response in asset and ultimately for growing global renewable energy needs. A scenario modeling approach was taken to analyze the impacts of the many technical and economic variables on financial performances. 20 distinct scenarios were designed, the baseline scenario developed is a traditional water based geothermal system by referring the setups in GEOPHIRES’ use case (a baseline from public, GEOPHIRES v2.0) to reflect a realistic commercial scale operation. The following 19 scenarios use CO2 as the working scenarios and are analyzed based on capital investment, operational costs, energy efficiency, and economic performance. Subsequent scenarios introduce modifications such as varying CO2 injection volumes and recovery rates, changes in subsurface storage capacity, system design parameters such as soak time and water-alternating-gas (WAG) ratios. The results indicate that the economic viability of CO₂-based systems is heavily influenced by several key factors. Using CO₂’s thermodynamic properties, such as lower viscosity and higher mobility does improve heat extraction, on the other side, its use greatly affects system costs where the majority of the costs come from CO2 transportation and storage. However, this heavily depends on regional carbon pricing mechanisms and infrastructures for potential asset and applications. Therefore, optimized injection strategies are necessary since they can reduce expenses and enhance energy recovery. In addition, CO₂ injection offers a secondary revenue opportunity through carbon storage credits under the 45Q tax incentive, further improving financial feasibility. Further improvements may come through technological advancements in CO2 handling and compression systems for recycling and reuse. The study concludes that while CO2-based geothermal systems offer distinct advantages, financial success hinges on effective CO2 management, fluid interactions of the stimulation, sweeping, and thermal exchange.
Topic: Enhanced Geothermal Systems