Thermodynamic analysis of power generation and waste heat recovery in CO2-plume geothermal systems in aquifers of varying heterogeneity

The International Energy Agency’s 2024 Global Hydrogen Review reported that hydrogen production reached 97 million metric tons in 2023, emitting around 920 million metric tons of CO 2 globally due to fossil-based methods. These significant emissions and others trigger the need to accelerate the integration of carbon capture, utilization, and storage (CCUS) technologies into industrial processes to produce low-carbon hydrogen and decarbonize the energy sector. By modeling 18 distinct aquifers, this research investigates the effects of horizontal permeability, anisotropy ratios, and heterogeneity on injectivity, heat extraction, plume migration, and CO 2 -plume geothermal (CPG) overall system performance. The study simulates fluid flow and power generation in multi-layered aquifers, considering both pumped and thermosiphon-based CPG systems. When excluding the CO 2 pumping requirement, the net electrical power reached close to 550 kW in high-permeability pumped systems and 100 kW in thermosiphon systems with the Organic Rankine Cycle (ORC). However, when including the CO 2 pumping requirements, the net power output dropped significantly across all the cases. The pumped systems scenarios achieve a cumulative power exceeding 50 GWh over 45 years, while thermosiphon systems often fall below zero. ORC integration enhances system performance, with cyclopentane and R-245FA demonstrating distinct advantages depending on the degree of aquifer thermal depletion. The result of this work indicates that pumped systems are more suitable for high-permeability aquifers where stable and prolonged high flow rates are achievable, while thermosiphon systems may be favored in settings where minimizing parasitic energy demand and operation duration are critical. Also, the results highlight the necessity of conducting a techno-economic assessment to justify CO 2 sequestration despite its energy penalties and the importance of rock and fluid properties for geothermal energy recovery. This research provides a base for future studies to improve the feasibility and scalability of CPG systems in diverse geological settings.