Ring trench collector: using geothermal energy efficiently

A ring trench collector is a pipe system consisting of long, flexible polyethylene plastic pipes (PE pipes). These pipes are laid in a spiral pattern in a narrow, ring-shaped trench around the house. At a depth of around 1.5 to 2 metres below the surface, this ground collector absorbs the geothermal energy and transfers it to your heat pump. At this depth, the ground maintains a stable temperature above freezing even in winter. This means that the collector provides reliable energy all year round – regardless of the weather or season.

Unlike deep drilling, you do not need large drilling equipment for the ring trench collector. This makes it cheaper and quicker to install. And the advantage over surface collectors is that it requires significantly less space. With this method, you can efficiently use geothermal energy – for heating, but also for cooling in summer.

The plastic pipes are laid in a trench at a depth of around 1.5 metres in overlapping loops around the house. They are filled with a frost-proof brine fluid. This absorbs the heat from the ground and transports it to the heat pump. There it is compressed and brought to a higher temperature level so that it can reliably heat your house.

What makes the ring trench collector so efficient?

• Extraction capacity: A ring trench collector achieves a high extraction capacity of heat from the ground with a small footprint.
• Annual performance factor: This type of collector achieves a high annual performance factor (APF), which means more heat from less electricity.
• Cooling: In summer, the system can also be used for passive cooling if dimensioned accordingly.

The ring trench collector in comparison:

• Ring trench collector or air heat pump? An air source heat pumpis easier to install, but is less efficient in very cold temperatures. A ring trench collector with a geothermal heat pump, on the other hand, uses geothermal energy, which remains stable throughout the year – this makes it more reliable and often cheaper in the long term. It is also quieter.
• Ring trench collector or deep borehole? – A deep borehole achieves similar constant performance, but is significantly more expensive and often requires a permit.

Planning and design are crucial to ensure that your system functions optimally. All of the following points play a role:

• Space requirements & required length: The system should be designed precisely for the heat pump and your house. The collector is dimensioned according to the calculated heating load. It is usually between 40 and 80 metres long. Buildings with higher heat requirements (e.g. unrenovated old buildings) require correspondingly longer collector pipes, which in turn require a larger trench area.
• Depth & width: It is common to lay the pipes at a depth of 1.5 to 2 metres. The width of the trench depends on whether the loops are laid vertically or horizontally. They are usually laid horizontally; the trench is then 1-2 metres wide. On smaller properties, it may be necessary to lay the loops vertically; in this case, the trench is only 50 cm wide.
• Trench layout: The trench is laid out in a ring shape at the edge of the property, at a minimum distance of one metre from the property boundary. This leaves the usable area in the middle free.
• Property size: Installation is also possible on small properties, as the loops of the trench pipes can be laid vertically in a space-saving manner in a ring trench around the house.
• Do-it-yourself installation: This is possible in principle, but requires specialist knowledge. We therefore recommendinstallation by trained specialists.
• Old buildings: Geothermal heat pumps and ring trench collectors can also be used in old buildings if there is sufficient space.
• Other points to consider when planning and installing a ring trench collector: Soil conditions, distance from the house, accessibility of the area, vegetation and any necessary permits

Overview of the components of the ring trench collector:

• Plastic pipes (usually PE pipes): flexible, durable and corrosion-resistant
• Brine fluid: frost-proof, serves as a heat transfer medium between the ground and the heat pump
• Trench: laid in a ring around the property, width and depth depending on the type of pipe loop installation.

Admittedly, this sounds like a lot of planning and work – but don't worry: with the right support, it's much easier than you think.

The cost of your ring trench collector depends on various factors – for example, the size of your property, the soil conditions and the required heating output. Basically, the price range is as follows:

• Planning, groundworks & materials: from approx. 6,000–8,000 €
• Complete with heat pump: from approx. 18,000–25,000 €

At first glance, this may seem like a significant investment. However, in the long term, you will save on heating costs thanks to the high efficiency of the ground source heat pump. And these savings are permanent, as the system has a service life of over 50 years and is virtually maintenance-free

A ring trench collector offers many advantages. Its high efficiency, long service life and eligibility for subsidies are particularly noteworthy. It is particularly suitable for new buildings, even those with smaller plots of land. There, it enables sustainable and cost-saving heating for decades. For existing buildings with very small plots of land or unfavourable soil, however, the disadvantages may outweigh the advantages. Here is a brief comparison of the advantages and disadvantages:

Advantages

• Very high efficiency and stable performance
• Sustainable and environmentally friendly due to low CO₂ emissions
• Can also be used for passive cooling
• Requires less space than flat-plate collectors
• Usually cheaper than deep drilling
• No permit required
• Eligible for government subsidies
• Durable (over 50 years) and low maintenance

Disadvantages

• Property must be freely accessible for construction work
• Earthworks are costly
• Not suitable for every property (soil conditions, e.g. rocky ground)

With a ring trench collector, you can use the natural energy source of the earth right on your doorstep – without any complicated drilling and with comparatively little space required.

This allows you to heat your home with a sustainable, efficient and independent heat source. Not only will you permanently reduce your heating costs, you will also be making an important contribution to climate protection.

Additional advantages of the ring trench collector are its long service life and the current government subsidies for heat pumps.

This type of heat generation is particularly suitable for new buildings with sufficient land area.

For old buildings or very small plots of land, implementing this heating solution can be more difficult, which is why it should be carefully considered on a case-by-case basis whether another heat pump solution is more suitable.

Use this overview to check whether a ring trench collector is suitable for your home:

• Property size: There is sufficient space around the house for a trench at least 1–2 metres wide. The greater the heating output required for the building, the longer and wider the collector must be designed. This is why unrenovated old buildings require more space than modern, well-insulated new buildings.
• Soil conditions: No solid rock or other subsoil that is difficult to excavate, but rather earth, sand or loam.
• Building type: Particularly suitable for new buildings with good insulation; in old buildings only if there is sufficient land area available for the longer collector pipes to cover the higher heat demand.
• Heating load: The required heat output of the house can be covered by the length of the collector.
• Access for groundworks: The property is accessible to excavators during the construction phase.
• Garden use: The area above the collector remains usable – accessible on foot and by vehicle, but without deep-rooted trees.
• Permits: In most cases, no complicated applications are necessary (unlike with deep drilling).

If most of these points apply to you, there is a very good chance that a ring trench collector is the right solution for your home.

Our experts are here to work together with you to find the best solution for your home or project.