Data Centers and Subsurface Thermal Energy Storage – Matching Data Center Cooling Needs with Recharging of Subsurface Thermal Energy Storage

This multi-lab, DOE-funded project addresses the significant energy and water consumption and cost to cool information technology (IT) equipment in data centers by utilizing subsurface thermal energy storage systems, more specifically, reservoir thermal energy storage (RTES). The project was augmented by an industrial advisory group (IAG), including experts from both the data center and subsurface energy storage sectors, to provide feedback. A scenario-based method was applied to perform techno-economic feasibility analysis based on three types of data centers covering a range of sizes and in three geographical locations. The techno-economic analysis (TEA) was performed to compare RTES scenarios with commonly used or most competitive non-RTES cooling scenarios. The main conclusions from the investigation are that all RTES systems studied are technically feasible and sustainable for at least a period of 20 years without major modifications of the RTES and IT cooling systems. Within the context of the assumptions made by this study, the key factor to make RTES for data center cooling economically feasible and attractive in the right location includes: 1) a shallow non-potable water-bearing geological formation with large transmissivity (thick and high permeability formation) to maximize storability and minimize the number and depth of wells needed; and 2) potential to use free (compressorless) or inexpensive cooling. Compressorless cooling can be provided by dry coolers in mild climates (although that is not the only option,) and inexpensive cooling can utilize compressor cooling when power costs are very low or negative (e.g., excessive renewable energy production). Future studies should further consider using chillers for RTES cooling (in addition to dry coolers) when there is a significant grid value to do so (large difference between peak and off-peak power cost). Additionally, system optimization should be performed for a specific site to maximize the benefit of using RTES for cooling when deployed. Additional benefits, such as resiliency during high heat events, are often not captured in traditional TEA studies, and should be considered.