Multi-Site Techno-Economic Analysis of Closed-Loop Geothermal Systems

The Closed Loop Geothermal Working Group (CLGWG) is a multi-lab collaborative consortium, funded by the U.S. Department of Energy Geothermal Technologies Office and focused on the techno-economics of closed loop systems for heating and power generation. The CLGWG has modeled U-loop and co-axial systems considering various technologies (e.g., vacuum-insulated tubing, multilaterals, enhanced near-wellbore thermal conductivity, flexible dispatch) and physical phenomena (e.g., non-steady temperature decline, background convective heat transfer, pressure and heat gain/loss, thermosiphon effect). In this work, we applied these models to 11 selected sites across the United States, classified into three geological categories: basin and range (e.g., Desert Peak, Roosevelt Hot Springs, Coso), volcanic regions (Newberry, Fenton Hill, Imperial Valley), and sedimentary basins (Eagle Ford, Haynesville, New York Appalachian, West Virginia Appalachian, Denver-Julesburg). For each site, we modeled the physical behavior using subsurface characteristics, including ambient temperature, geothermal gradient, target depth, and rock properties (e.g., density, permeability, thermal conductivity, specific heat capacity) for different closed-loop designs. We found significant variability in economic competitiveness across sites, particularly impacted by mass flow rate of the working fluid, drilling cost, and drilling depth. Separately, on-the-fly simulations and convective models were integrated into GeoCLUSTER, an open-source web simulator that enables closed loop developers, investors, and enthusiasts to analyze closed loop designs across different surface and subsurface settings.