Kian Khaksar, Saeed Vadiee and Biao Li of Concordia University describe in Renewable Energy (DOI 10.1016/j.renene.2026.126502) a numerical model of a standing column well (SCW). In this type of well the borehole is connected both hydraulically and thermally to the surrounding rock, so a single, compact well can exchange a large amount of heat. The authors note that its behaviour depends heavily on the hydraulic conditions underground and on how the well is operated.
Method
The team developed a coupled thermal-hydraulic model of an SCW system. They validated it with data from a field thermal response test and then ran it for a case typical of the study area. A parametric study tested how five factors affect thermal and hydraulic behaviour: aquifer permeability, the share of water bled off, well radius, the temperature of the reinjected water, and depth.
Results
Permeability determines whether the well relies mainly on heat conduction or on groundwater inflow. Where permeability is low, heat moves by conduction unless bleeding draws water in from the aquifer. Where it is high, exchange with groundwater raises the thermal output and turns the influence of well geometry the other way round.
Wider wells favour conduction, while narrower ones increase inflow from the aquifer and the heat delivered. Drilling deeper brings a small gain when conduction dominates, but a marked increase in output when the aquifer is actively exchanging water with the well. Bleeding helps in both cases, though the resulting drop in the water table limits operation. These patterns held over a 120-day period, and the authors quantified the loss of performance.
As water rises through the riser pipe, thermal short-circuiting cuts the temperature gain achieved in the annulus by roughly 9-13 percent.
What it means for practice
According to the authors, SCW design should account for the hydraulic link between the well and the aquifer, the way bleeding is managed, and the geometry of the well.
