The technology

What are geothermal heat pumps?

Geothermal heat pumps (also called Ground Source Heat Pumps, GSHP) are an established technology for space heating and cooling and sanitary hot water that makes use of shallow geothermal energy. Shallow geothermal means energy stored in the form of heat beneath the earth’s surface at depths between 0 and 500m.

Geothermal heat pumps systems have three main components:

  • The ground side, to get heat out of or into the ground;
  • The heat pump itself, to convert that heat to a suitable temperature level;
  • The building side, i.e. the equipment inside the building that transfers the heat or cold into the rooms.

There are two main types of systems used to connect the underground heat to the building system:

  • Open-loop systems, where the main heat carrier, ground water, flows freely in the underground and it is directly used through ground water wells.
  • Closed-loop systems, that use heat exchangers placed in the underground. There are several types, such as: horizontal loops; borehole heat exchangers (BHE); compact forms of ground heat exchangers; thermo-active structures (pipes in any kind of building element in contact with the ground); etc.

A good design must take care of the whole system, matching the components in such a way that the most effective operation and the highest level of comfort can be achieved. To choose the right system for a specific installation, several factors have to be considered, mainly:

  • The climatic zone;
  • The thermal and hydraulic parameters on site;
  • The heating and cooling characteristics of the building(s).

The different natural ground temperatures throughout Europe, from 2-3° near the polar circle to about 20° in the very south of Europe, have a great influence on the options and design for shallow geothermal installations.

Geothermal heat pumps applications

Shallow geothermal systems are very versatile and can be adapted to almost every subsurface condition. They can be used in different kind of structures, from small, residential houses to large individual buildings or complexes of buildings, such as offices, hotels, schools, shopping centres, and so on.

The residential sector generally employs heat pumps produced in larger series and with standard heating capacities from ca. 5 to 20 kW, while for the commercial sector the installation tends to be much larger.

For large complexes, heat pumps with capacities from ca. 50 kW upwards are usually constructed individually or in smaller numbers, and adapted to the specific site conditions.

Often buildings have a rather unbalanced heating and cooling demand, either given by their climatic surroundings (very cold or very warm climates), or by the specific use of the building (there are, for example, shopping malls that require virtually no heating but a lot of cooling). In these cases, hybrid systems are designed to cover as much load as possible from the geothermal system and to balance the heat in the underground through separate sources, like cold air in winter or at night time, waste heat, solar heat, and so on.

Using all the different options available to geothermal design allows for small and large, energy efficient, economic, and reliable installations all over Europe.

Many innovative, cutting edge architectural designs have chosen geothermal heat pumps for their highly efficient and highly versatile nature.

To discover examples of the wide range of geothermal heat pumps applications, visit the Projects Showcase.