Closed Loop Geothermal Analysis Modeling and Simulation Using Idaho National Laboratory’ RELAP5-3D-FALCON Coupled Codes

Abstract

In the framework of the U.S. Department of Energy (DOE) “Geothermal Closed Loop” project, Idaho National Laboratory (INL) has developed a new software suite for the analysis of geothermal systems. The software suite is based on two INL codes, RELAP5-3D and FALCON, coupled via a dedicated Python-based software interface. RELAP5-3D is a well-established two-phase system thermal-hydraulic code with nuclear pedigree, based on a nonhomogeneous and nonequilibrium model for the two-phase system, and it allows a detailed analysis of two-phase networks. FALCON is a MOOSE-based application (a finite element framework designed in object-oriented C++) for simulating fully coupled thermal-hydraulic-mechanical-chemical (THMC) based on finite element methods processes in subsurface systems. During Fiscal Year 2022, we have optimized the coupling interface, and analyzed two closed-loop configurations, based on a central well and multiple descending/ascending legs. INL INEL-1 well and Utah-FORGE sites, hot-dry rock domains, have been used for defining the boundary conditions for the analysis. Reference solutions with systems performance are obtained as function of coolant mass flow, and number of legs.