Radial Closed-Loop Geothermal Architectures for Phased Scaling: Thermal Performance Study

Abstract

Next-generation geothermal systems are advancing along two primary pathways: Enhanced Geothermal Systems (EGS) which create convective reservoirs via hydraulic fracturing, and Advanced Geothermal Systems (AGS), which extract heat via conduction through closed loops. While EGS offers high energy yields, it carries risks of induced seismicity and geological uncertainty. Conversely, conduction-based closed-loop systems mitigate seismicity, but face challenges related to thermal drawdown (short-circuiting) between proximal laterals and complex well-to-well interceptions. This paper introduces and evaluates the Telluric Radial System (TRS), a hub-and-spoke topology designed to synthesize the massive reservoir contact area of EGS with the low environmental risk of conductive systems. The architecture consists of a large-diameter, insulated central injection hub feeding a distributed network of single-layer, radially oriented production satellites. This configuration is hypothesized to offer superior geometric efficiency by eliminating the vertical thermal interference inherent in stacked parallel loop designs and accessing a larger volume of fresh rock, while consolidating well interception by targeting a stationary vertical hub. Furthermore, the design enables a phased scaling development model, allowing individual satellite radiators to be commissioned sequentially to stage risk and capital deployment. This study presents the conceptual framework and a comparative thermal performance analysis using 3D finite element modeling in OpenGeoSys utilizing parameters modeling the Malm Carbonate formation in Geretsried, Germany. Simulations were normalized for total drilling length to ensure an accurate comparison between radiator topologies. Results demonstrate that the single-layer TRS radiator maintains outlet temperatures 2°C to 5°C higher than equivalent multi-lateral stacked designs over a 30-year operational life, confirming that radial fanning effectively mitigates far-field thermal drawdown despite localized convergence at the hub. The model is further used to explore the system's sensitivity to key design parameters, including radial well spacing and the thermal resistance of the injector's insulation. This work provides a foundational assessment of the TRS as a pathway for developing scalable and dispatchable geothermal assets.