Heat pumps: energy from the deep

Jürg Zulliger

Without thinking too much about it, would you be able to explain to a friend how heat pumps work? In their day-to-day life, many people are used to dealing with water or air pumps – but heat pumps? Let’s make it a little simpler: heat pumps work similarly to the cooling system in your fridge at home. Electrically-powered compressors raise the temperature and in doing so, they supply heating energy for buildings.

Types of heat pumps

Geothermal probes are used to make use of the heat that is present under the surface of the earth. Even on the coldest winter days there is often 5 to 10 degrees of heat at a depth of 250 to 300 metres (depending on the region and geology present). Depending on the model, heat pumps draw heat from the soil, from the surrounding rocks or from the groundwater. The energy is then conducted to the surface or into the heating system via a medium.

• Brine-water heat pump: A probe positioned at a depth of 50 to 300 metres draws the heat from the ground.
• Water-water heat pumps: make use of heat from groundwater or surface water.
• Air heat pumps: these pumps draw heat from the surrounding air and do not require any drilling

Heat pumps “What do I need to know?”

Heat pumps that create energy from the subsoil (brine-water) are particularly sustainable and efficient.  As is always the case when dealing with building, energy or modern facility engineering, it pays to have planned well. Ask yourself: what can be done at the site in question?

Andreas Baumgartner, senior consultant at the engineering company Amstein + Walthert had the following to say on the topic: “In densely built-up areas especially, you need to carefully consider what needs to be in place to permit a building to be retrofitted with a heat pump.”

One of the things you need to consider is the small amount of space that might be available. If you opt for the more expensive but more sustainable brine-water variant then you’ll need to consider whether probe drilling can be carried out on that property. Will the installer and the drilling company be easily able to use all their equipment and install everything that they need on-site?

You also need to consider your budget before you enter the planning stage. These days, many builders get their initial information from the internet or from catalogues. The expert Baumgartner said: “It is possible to buy a heat pump for a price of perhaps 12,000 Francs.

But with all the adaptations, building measures, connections and possible special drilling that may be needed, the final bill tends to be much more expensive than was thought. As a rule of thumb, the price for a detached house tends to be between 30,000 to 55,000 Francs for the planning, installation, heat pump and geothermal probe drilling. For larger buildings and apartment blocks or where particular geological problems are present, it can be more expensive.