Heat transport simulations in a heterogeneous aquifer used for aquifer thermal energy storage (ATES)

Abstract

A modelling study was carried out to evaluate the influence of aquifer heterogeneity, as represented by geologic layering, on heat transport and storage in an aquifer used for aquifer thermal energy storage (ATES). An existing ATES system in Agassiz, British Columbia, Canada, was used as a case study. The system consists of four production wells completed in an unconfined heterogeneous aquifer consisting of interbedded sands and gravels. An additional dump well was installed to provide for heat dissipation during the peak cooling periods. Three monitoring wells and the production wells were logged for temperature periodically within the first 1.5 years of operation. A three-dimensional groundwater flow and heat transport model was developed using FEFLOW. Simulation results indicate that heat and (or) cold energy moved preferentially in discrete zones within the aquifer or at least entered the wells over discrete intervals. Monitoring data support model results, but show that thermal storage was successfully achieved despite a significant cooling operation during the first year.

Optimization and spatial pattern of large-scale aquifer thermal energy storage

“…In this range, the effect of temperature dependency of groundwater viscosity and density on the performance of the ATES can be neglected [42][43][44][45] such that the heat transport processes (advection, conduction and dispersion) are linear with temperature. As long as the difference between the injection temperatures in summer and winter with the ambient aquifer temperature are equal, g t becomes independent of injection temperatures.…”

“…Several other Table 3 Optimal performance and pattern for the case Amsterdam and mean ± 1 standard deviation from the sensitivity analysis. uncertainties that are not included in our analysis need also to be considered, namely: aquifer heterogeneity creating preferential flow and increased thermal interference [15,42], or variability in energy demand. Due to these factors, it could be argued to select well distances somewhat larger than the well distances obtained in our optimization.…”

Numerical analysis of coupled thermo-hydraulic problems in geotechnical engineering

“…Spacing of the wells is a particularly important aspect of the design of 39 open-loop systems. If the wells are too close, the thermal plume of cold or warm water from the 40 injection well may reach the abstraction well and reduce the efficiency of the system [1] and Bridger and Allen [9], amongst others, to simulate open-loop systems. However, the details of the 8 FE analysis, particularly in terms of the numerical method or the boundary conditions, have been the 9 subject of limited discussion.…”

“…Combining Equations ( 2 ), ( 3 ) and ( 9 ) To validate the coupled thermo-hydraulic finite element formulation, several analyses on a 1 m bar of 5 soil with element length of 0.01 m, subjected to one-dimensional (1D) convection-dominated heat 6 transfer, were conducted in ICFEP using 4-noded linear quadrilateral two-dimensional (2D) elements. 7…”

“…7 4 FE analysis of highly convective heat transfer 8 4.1 Péclet number 9 In coupled thermo-hydraulic problems, the heat flux is often characterised in terms of a Péclet number 10 (Pe), which represents the ratio between the convective and the conductive transport rates. A low 11…”