Ground Source Heat Pumps: Principle of Operation and Benefits

Heat pumps represent a highly efficient solution for alternative heating in modern homes. They not only provide significant savings on utility bills but also ensure energy independence while protecting the environment.

What is a Ground Source Heat Pump?

A ground source heat pump (GSHP) is a geothermal system that extracts low-grade thermal energy from the earth and converts it into high-grade heat for space heating and domestic hot water. Its primary advantage is a stable Coefficient of Performance (COP 1:4–4.5) year-round, as soil temperatures below 15 meters remain constant (approx. +10°C) regardless of outdoor weather conditions.

Ground source heat pump system diagram for home heating

During the warm season, the upper layers of the soil accumulate solar heat. At a depth of about 2 meters, temperatures fluctuate between +7°C and +13°C. This must be considered when calculating equipment capacity and choosing the installation method for horizontal collectors. To extract this energy, specialized pipes are buried in the ground to circulate a heat transfer fluid.

Geothermal System Components

A ground source heat pump consists of two primary sections:

Indoor Unit: The main module installed in the plant room (boiler room), where heat is intensified and transferred to the home's heating circuit.
Outdoor Loop: A network of pipes buried in the ground where the fluid continuously circulates and absorbs energy from the earth.

Types of Outdoor Collectors: Horizontal vs. Vertical

The system operates based on the Carnot cycle: a refrigerant evaporates by absorbing ground heat and, after being compressed, releases that heat into the building's heating circuit upon condensation.

1. Horizontal Collector
This method is more cost-effective in terms of installation but requires a large open area of land. The average heat extraction is approximately 20 W/m. It is crucial to maintain a pipe spacing of at least 0.7m and account for soil moisture levels.

2. Vertical Probe (Borehole)
A compact solution offering the most stable efficiency. Pipes are placed in boreholes ranging from 20 to 300 meters deep. The space between the pipe and the ground is filled with thermally enhanced grout (bentonite) to maximize heat transfer. Despite higher initial drilling costs, this system is highly durable and does not occupy useful surface area.

Thinking about installing a heat pump?

It is vital to plan the installation during the initial design phase of the house. This ensures proper site planning, as trees or large structures cannot be placed directly over the loop network (a lawn or garden is ideal).

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