Techno-Economics of Co-Axial Geothermal Systems Equipped with Vacuum-Insulated Tubing

This study presents a field-validated techno-economic evaluation of co-axial closed-loop geothermal systems equipped with vacuum-insulated tubing (VIT) for electricity generation. Using field data from a full-scale 3,510-meter test well drilled by National Oilwell Varco (NOV) and completed with VIT, we validated the Slender-Body Theory (SBT) model for transient heat conduction in co-axial systems wellbores. The validated SBT model was integrated into the Flexible Geothermal Economics Modeling (FGEM) tool to evaluate lifecycle performance under variable conditions. A base case scenario, consisting often 7-km wells feeding into a 2 MWe air-cooled binary power plant, was considered to evaluate lifecycle economics. The system achieved an LCOE of 643 USD/MWhe considering drilling cost of 1,800 USD/meter. Sensitivity analysis also revealed that flow rate, rock thermal conductivity, VIT insulation, drilling cost, and discount rate significantly influence economic outcomes. Drilling cost was found to be the most significant economics driver, where LCOE was <100 USD/MWhe under optimistic drilling cost scenarios of 100 USD/meter. Additionally, results indicated that highly insulated VIT, optimized flow rates, and favorable in-situ rock thermal conductivity were crucial to unlocking cost-effective geothermal power using co-axial closed loop configurations.