Geological Suitability of Aquifer Thermal Energy Storage in the Durham Sub-Basin

Abstract

This study evaluates the geological suitability of the subsurface geology of the Durham Triassic sub-basin at Duke University for the implementation of an Aquifer Thermal Energy Storage system. The proposed project would capture excess electricity-driven heat produced by chiller plants on Duke's campus during the summer. This heat would be transferred to a water source using a heat exchanger, and the heated water would then be pumped underground for storage until winter. During the winter, the stored hot water would be pumped back up and used as a supplemental heat source for campus buildings which are currently heated by CO2 producing natural gas. To assess ATES potential, cores drilled from a 202-meter (666-foot) borehole on Duke's central campus drill site were analyzed. In addition, we collected hand samples from nearby outcrops in the Durham sub-basin and created rock thin sections to determine mineralogy and sediment characteristics including grain size and porosity. We found sequences of sandstone layers in the core that were 1-5 meters thick. We also found a range of porosities from outcrop hand samples (median porosity 8.2% ±5.9%). Preliminary pumping tests suggest low flow rate (~0.03-10 gallons per minute) could impede ATES potential in the Durham sub-basin. By understanding the geological characteristics of the site, we can better understand what it would take to tailor and optimize the design and operation of the ATES system for maximum energy storage. The project will study Durham sub-basin geology to determine suitability for a proof-of-concept ATES system to facilitate targeted deployment across the Durham region for communities in need.