| Abstract |
As fossil fuel-based energy sources are replaced by Variable Renewable Energy (VRE) technologies, efficient long-duration energy storage solutions are critical to managing seasonal variations in VRE generation and consumption. Geologic Thermal Energy Storage (GeoTES) offers a promising long-duration storage solution, helping to balance differing summer and winter energy demands and providing lower levelized costs of storage (LCOS) compared to other thermal storage options. In 2024-2025, teams at the National Renewable Energy Laboratory (NREL), Idaho National Laboratory (INL), and Lawrence Berkeley National Laboratory (LBNL) successfully identified suitable GeoTES reservoirs, examined GeoTES systems charged by concentrating solar power (CSP) and renewable electricity via heat pumps (Carnot Battery), and validated a techno-economic analysis (TEA) model for GeoTES. In 2026, Idaho National Laboratory (INL) conducted extensive subsurface characterization at selected GeoTES sites in Texas and California, involving geological evaluations and site-wide lithological and hydrogeological characterization through the mining and digitization of existing geological data. The collected data facilitated the construction of a detailed 3D geological model, enabling visualization and assessment of reservoir heterogeneity, lithology, fault structures, and potential leakage pathways. Reactive transport modeling and reservoir simulations demonstrate the viability of these sites for both storing and extracting heat in the subsurface, highlighting the critical role of advanced geological modeling and simulation in developing promising large scale, long-duration energy storage solutions. |