Horizontal collector (ground collector)

A horizontal collector is a pipe network just below the surface of the ground, through which a geothermal heat pump extracts heat from the garden. It requires a lot of space.

With a horizontal collector, also known as a flat or ground collector, plastic pipes are laid horizontally in the ground, usually over a large area in the garden. A frost-resistant liquid, the brine, circulates inside them. It absorbs heat from the ground and transfers it to the brine-to-water heat pump.

Where the heat comes from

According to klimaaktiv, flat collectors primarily use heat stored in the top layer of soil by the sun, rain and warm ambient air. One variant is the trench collector, where the pipes are laid in trenches.

Space requirements and design

The klimaaktiv guide specifies that ground collectors may be designed for a maximum of 25 W per m² of ground area. Higher values are only permitted with a geological survey. This means: the greater the heating load of your house, the more garden space you need. Because the collector relies primarily on sun and rain, you should also ask your designer whether and how the area above it may be used or paved later on.

Permit

Depending on the federal state and location, a water rights permit or notification may be required. In Upper Austria, for example, flat collectors in specially protected water areas and in settlements without a central water supply require a permit. Clarify this early on with your Bezirkshauptmannschaft (district commission) or the Gemeindeamt (municipal office).

You can read about whether a collector, borehole or air is a better fit in Air or geothermal energy.

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