Energy pile

A foundation that heats the building

An energy pile does double duty: it carries the structure and acts as a ground heat exchanger. Terra Multiphysics tracks the structural pile and its heat exchange together — soil–structure interaction included.

0.04–0.08 °C
mean error vs instrumented field data
20 days
continuous operating run
3 modes
8 h, 16 h and 24 h operation
Model definition

What the model solves

SystemSingle energy pile with three U-loop circuits
CouplingThermo-hydro-mechanical (heat, pore-fluid flow, ground deformation, with soil–structure interaction)
Validation referenceInstrumented field test, Faizal et al. (2016)
Operating modes8 h, 16 h, and 24 h continuous extraction
Run duration20 days
Output trackedDaily circulating-fluid outlet temperature
Agreement vs measured0.04 to 0.08 °C mean absolute error after one global outlet-offset calibration across the three operating modes
Validation

Matched to an instrumented field record

Daily outlet temperature against an instrumented three-loop energy pile, across three operating modes over 20 days.

20-day field record

Daily outlet temperature, three operating modes

Solid curves are Terra calibrated outlet response; points are the digitized field record.

0.088 h MAE (°C) 0.0716 h MAE (°C) 0.0424 h MAE (°C)
8 h on / 16 h off 16 h on / 8 h off 24 h continuous measured points
In-situ field validation. Daily outlet temperature against the instrumented three-loop energy pile of Faizal et al. (2016), across three operating modes over 20 days: 0.04 to 0.08 °C mean absolute error after one global outlet-offset calibration (+0.36 °C).
Thermo-mechanical response

Heating moves the foundation

A full-scale heating test shows the structural side of an energy pile: the temperature rises, the head heaves, and both recover together.

28-day heating test

Temperature rise and pile-head heave on one timeline

The heating phase and recovery phase share the same time scale, so the structural response is visible beside the thermal load.

20.7sim peak ΔT (°C) 3.58sim peak heave (mm) 0.32heave RMSE (mm)
Terra temperature Terra heave in-situ record heating recovery
Field-scale thermo-mechanical validation. The pile temperature tracks the in-situ record (peak +20.7 vs +22.0 °C), and the calibrated head response follows the measured heave-and-recovery curve (peak +3.58 vs +3.58 mm, residual +0.79 vs +0.79 mm, RMSE 0.32 mm).
What it captures

The coupling simpler models leave out

A foundation pile carries the building and exchanges heat with the ground at the same time. The surrounding soil sits at a near-constant temperature year-round, so the pile can borrow that warmth in winter or dump heat into it in summer. Modelling it well means solving heat, pore-water flow and ground deformation together — not one at a time.

Terra resolves the full coupled thermo-hydro-mechanical response: the carrier fluid in the embedded U-loop, the heat exchange across the pipe and pile, the cooling plume in the soil, and the thermal expansion and contraction the cycling drives in the pile and ground. That soil–structure interaction is the coupled signature a temperature-only model cannot capture, and the calibrated daily outlet response tracks the measured field record to 0.04–0.08 °C MAE.

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