Analytical solutions for aquifer thermal energy storage

Abstract

The concept of aquifer thermal energy storage involves injection of water at elevated temperature, and possibly nonambient salinity, into a host aquifer. We consider axisymmetric injection, wherein both the composition and temperature of the injected fluid differ from the fluid in the target aquifer. In this setting, we derive the governing equations within a vertically integrated framework, and show their self‐similar structure. We subsequently derive explicit approximate solutions to the self‐similar equations for parameter ranges of relevance to thermal energy storage (small density and viscosity differences). The analysis is supported by numerical validation, covering the relevant parameter regime. The resulting comparisons demonstrate the mathematical qualities of the analytical approximations. A study based on field data from analogue sites justifies the assertions regarding the magnitude of the dimensionless parameters used in the analysis.