Geological Thermal Energy Storage for Urban Centers

Abstract:

For much of the conterminous USA, saline or brackish aquifers underlie regional potable groundwater systems. A non-consumptive use for these relatively low-quality groundwater systems is the seasonal storage of hot or cold water for later use (called reservoir thermal energy storage; RTES). For example, cold water can be stored during the winter, then extracted in the summer for cooling, or conversely, summer heat can be stored and used during the winter. We summarize the results of a recent study (Burns and others, 2020) where broadly applicable methods are developed and applied to the Columbia River Basalt Group (CRBG) beneath the Portland Basin, Oregon, USA. RTES is shown to be feasible for heating a large medical research building on the Oregon Health and Science University South Waterfront campus (~1.9 GWh annual heat load). Unlike most geothermal energy resources where efficiency decreases as the system is cooled, RTES efficiency increases over time as the reservoir approaches the optimal storage temperature (hot or cold). Analytic solutions are developed to evaluate efficacy for new study areas and to aid in the design of RTES systems (e.g., well-spacing, thermal source sizing, etc.). Regional maps of thermal energy storage capacity can be produced. For the CRBG beneath the Portland Basin, total annual storage capacity of the Portland Basin is estimated to be 43,400 GWh (assuming a 10 °C temperature differential can be stored and extracted seasonally), indicating a tremendous heating and cooling potential (>10,000 large buildings).

Burns, E.R., Bershaw, J., Williams, C.F., Wells, R., Uddenberg, M., Scanlon, D., Cladouhos, T.T., and van Houten, B., 2020, Using Saline or Brackish Aquifers as Reservoirs for Thermal Energy Storage, with Example Calculations for Direct-Use Heating in the Portland Basin, OR, USA, Geothermics, v. 88, 101877, 17 p. https://doi.org/10.1016/j.geothermics.2020.101877