Numerical Modeling of the Interference of Thermally Unbalanced Aquifer Thermal Energy Storage Systems in Brussels (Belgium)

Abstract

A numerical model was built using FEFLOW® to simulate groundwater flow and heat transport in a confined aquifer in Brussels where two Aquifer Thermal Energy Storage (ATES) systems were installed. These systems are operating in adjacent buildings and exploit the same aquifer made up of mixed sandy and silty sublayers. The model was calibrated for groundwater flow and partially for heat transport. Several scenarios were considered to determine if the two ATES systems were interfering. The results showed that a significant imbalance between the injection of warm and cold water in the first installed ATES system led to the occurrence of a heat plume spreading more and more over the years. This plume eventually reached the cold wells of the same installation. The temperature, therefore, increased in warm and cold wells and the efficiency of the building’s cooling system decreased. When the second ATES system began to be operational, the simulated results showed that, even if the heat plumes of the two systems had come into contact, the influence of the second system on the first one was negligible during the first two years of joint operation. For a longer modeled period, simulated results pointed out that the joint operation of the two ATES systems was not adapted to balance, in the long term, the quantity of warm and cold water injected in the aquifer. The groundwater temperature would rise inexorably in the warm and cold wells of both systems. The heat plumes would spread more and more over the years at the expense of the efficiency of both systems, especially concerning building’s cooling with stored cold groundwater.

Modelling Interactions between Three Aquifer Thermal Energy Storage (ATES) Systems in Brussels (Belgium)

“…Here, we will demonstrate that even though one unbalanced ATES system partly jeopardizes the thermal state of the upper aquifer [3], an adjacent but deeper ATES system can operate without too many negative interactions limiting either efficiency or durability. The numerical simulation of the 3D groundwater flow and heat transport conditions considering the upper and deeper aquifers separated by the aquitard provide an excellent tool for analysis and decision support.…”

“…In very simplified and theoretical situations, the cold and hot plumes can be calculated using analytical solutions [12,13]. The complexity of actual heterogeneous hydrogeological conditions combined with the locations of the wells makes the use of coupled groundwater flow and heat transport numerical models essential [3,[14][15][16][17][18][19][20][21][22][23].…”

“…In summer, groundwater is pumped into a (cold) well for cooling, and the heat is injected back with water into the aquifer at a higher temperature using a (warm) well. In winter, the system provides heat to the building from the pumped groundwater, and injection occurs at a lower temperature [1][2][3]. Both the Appl.…”

“…The objective of this paper is to examine the cumulative effect of three adjacent open geothermal systems. A first model including a single aquifer, exploited by two of the three ATES systems, was developed previously by Bulté et al [3], who studied the possible interference between these two systems. Here we add a deep aquifer separated from the upper aquifer by an aquitard (i.e., a low hydraulic conductivity layer) that is exploited by a newly added ATES system requiring a power of about 950 kW for both the cold and the warm seasons.…”

Retrofitting for Improving Indoor Air Quality and Energy Efficiency in the Hospital Building

“…It is friendly to the environment and helps bring about a sizeable reduction in carbon dioxide emissions produced. Bulté et al [40] Solar-powered cooling systems for hospitals.…”