InterPore2026

Double Diffusive Convection in Aquifer Thermal Energy Storage (ATES) Systems

22 May 2026, 10:20

1h 30m

Poster Presentation (MS01) Porous Media for a Green World: Energy & Climate Poster

Speaker

Tarun Jain (University of Alberta, Canada)

Description

Aquifer thermal energy storage (ATES) system is a sustainable energy storage technology for long-term recovery of stored heat and has the potential of reducing global carbon emissions. Across the globe, many low-temperature aquifer thermal energy storage (LT-ATES) systems with injected water temperatures of less than 60°C have been engineered for direct applications in building heating during adverse thermal conditions [1]. However, due to their low-temperature delivery, LT-ATES are often coupled with ground-source heat pumps (GSHPs) to mitigate their deficiencies. High-temperature aquifer thermal energy storage (HT-ATES) is an advancement on the low-temperature storage, where hot water with temperatures exceeding 60°C is injected into aquifers to store seasonal thermal energy and recover it later. Across literature, they have been reported to potentially deliver high thermal energy recovery during extraction and can be directly deployed at industrial scales, in addition to building heating applications. However, only a few pilot projects exist alongside theoretical studies, which report that free thermal convection is one of the major impediments to harnessing the potential of HT-ATES [2]. Injected hot water, being less dense than the native aquifer fluid, flows farther distances due to buoyant convection, which is further enhanced in the case of HT-ATES, leading to a drastic loss in the recovery efficiency. To reduce thermal energy losses, van Lopik et al. (2016) suggest adding salinity to eliminate the density disparity between the injected and native fluids, thereby reducing buoyant convection [3]. In their numerical analysis, they demonstrate a more vertical fluid-fluid interface that preserves the injected fluid near the injection well, while also reducing diffusive losses between the injected and native fluids, as well as between the injected fluid and the surrounding rocks. They report a recovery efficiency of 69%, which is a significant increase from the non-salinity counterparts of the efficiency of about 45% [2, 3].
While the distinct diffusive behaviours of salt and heat lead to a transient change in the density of the injected fluid, they also lead to the onset of double-diffusive instabilities. Based on the injection conditions and the relative concentration of the two species, flow is influenced by either fingering instability or layered convection (see Figure 1) [4]. A common metric used to define this type of convection is the Stability ratio N=βΔC/αΔT, which dictates layered convection for N > 1 and fingered convection for N < 1. Such double-diffusive effects may alter the energy dynamics of an ATES system, thereby demonstrating efficiencies different from those reported in the literature. In our study, we investigate the double-diffusive convection in both LT-ATES and HT-ATES to assess its potential impact on thermal energy recovery. We approach the problem by simulating a small-scale injection-storage-recovery model, which enables us to understand the dynamics of flow and energy resulting from the varying thermohydraulic properties of the aquifers and the injection-recovery methods. We decompose the total injected energy into kinetic and potential components and include additional loss terms, scaled to quantify their relative influence on the thermal recovery efficiency [5].