A ground heat exchanger is a network of buried pipes through which a heat-transfer fluid circulates to absorb thermal energy from the ground or release heat into it. It forms the earth-side component of a ground source heat pump system.
How It Works
The ground maintains a nearly constant temperature below the frost line. A ground heat exchanger exploits this by circulating a mixture of water and antifreeze through its pipe loop:
- Heating mode — the fluid absorbs warmth from the surrounding soil and carries it to the heat pump, which raises the temperature for space heating or hot water
- Cooling mode — excess heat from the building is transferred into the ground for storage or dissipation
The efficiency of the system depends on soil conductivity, loop length, and the temperature difference between the fluid and the ground.
Types of Ground Heat Exchangers
- Horizontal loops — pipes laid in trenches at 1.2 to 2 metres deep, requiring a generous land area
- Vertical boreholes — pipes inserted into boreholes drilled 50 to 200 metres deep, ideal for limited surface space
- Slinky coils — coiled pipe loops placed in shorter trenches to increase surface contact in a compact area
- Energy baskets — spiral or cage-shaped exchangers buried in pits, a middle ground between horizontal and vertical
Application
Ground heat exchangers are used in residential, commercial, and institutional buildings as part of sustainable heating and cooling systems. Key applications include:
- New-build homes paired with underfloor heating
- Schools, hospitals, and office buildings seeking low-carbon HVAC
- District heating networks serving multiple buildings from shared boreholes
- Seasonal thermal energy storage projects
Design requires a thermal response test and careful sizing to match the building’s peak heating and cooling loads over its lifetime.
Related Terms
- Ground source energy
- Heat pump
- Thermal response test
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