Progress on Geological Thermal Energy Storage Analysis

Geological thermal energy storage (GeoTES) utilizes subsurface reservoirs to store thermal energy for power generation and direct-use heating and cooling. GeoTES has emerged as a promising long-duration, grid-scale solution, providing stability and security through flexible operations and valuable grid services. This approach significantly enhances the use of low-temperature reservoirs, which would otherwise be unsuitable for geothermal power plants. It also leverages depleted oil and gas reservoirs, concentrating solar power, variable renewables (photovoltaic and wind), and geothermal-related power cycles. Previous work has indicated that GeoTES has low marginal costs of energy storage capacity, making it particularly competitive for seasonal, grid-scale dispatch. In this article, we will describe progress made by a consortium of national laboratories and industry organizations on the analysis and development of GeoTES. The article will describe the latest techno-economic models which evaluate the cost, performance, and energy storage potential of GeoTES, as well as "demand-led" models that evaluate the potential for long-duration energy storage systems in different energy mix scenarios. We discuss progress made on Thermal-Hydraulic-Mechanical-Chemical subsurface models of specific sites of interest to industry developers and introduce concepts that can be used to develop experimental procedures for analyzing geochemical aspects. We describe industry perspectives which have categorized and characterized a range of risks and mitigation strategies that may impact the deployment of GeoTES.