Date of Award
8-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Environmental Engineering and Earth Science
Committee Chair/Advisor
Ronald Falta
Committee Member
Lawrence Murdoch
Committee Member
Scott Brame
Abstract
A pilot-scale high-temperature thermal energy storage site has been developed at Clemson University and began operation in April 2025. High-temperature heat transfer fluid is circulated through a hexagonal array of borehole heat exchangers, which are installed up to 35 ft deep in the subsurface. The thermal energy is stored in the ground and is extracted by circulating the heat transfer fluid at a lower temperature. This test was expected to last more than six months and there was no way to evaluate the temperature data being measured. Since only temperature was being monitored, it was difficult to predict when key milestones were met, such as when the subsurface reaches boiling point or when the subsurface dries out, and what factors affected them.
The objective of this thesis is to develop a better understanding of the processes occurring during high-temperature heat storage and to guide decisions during operation. This was accomplished by using TOUGH2 (Transport of Unsaturated Groundwater and Heat; Pruess et al., 2012), a multiphase flow and heat transfer code, to simulate subsurface energy storage. The model was calibrated to field data based on existing parameters (Taylor, 2001) and produced modeled subsurface temperatures within 5% of observed data.
The calibrated model offers insights on multiphase flow and heat transfer in the system during heating and cooling, when boiling and superheated vapor conditions are reached, and can estimate the thermal power delivered and produced from the system. The simulations show the extent of the dry core created during heating as well as the water flow response when heat input stopped. The proximity to the water table limited the vertical extent of high temperatures and led to more water flowing into the dry core. The total mass removed from the system can be modeled, something that was difficult to measure in the field. Explanations for observed phenomena, such as evaporative cooling, were supported with results from the model.
Recommended Citation
Jennings, Samuel R., "Evaluation of High Temperature Thermal Energy Storage at a Field Site" (2026). All Theses. 4826.
https://open.clemson.edu/all_theses/4826