Essentially the role of heat exchangers is to transfer the heat of a flowing material to another flowing material with a lower starting temperature. The materials can be gaseous or liquid. The temperature difference between the two media as the driving differential is essential for heat transfer.
Shallow geothermal energy is based on the same fundamental principle as solar thermal energy. However, in this case it is the ground which is acting as a heat source, not the sun. There is an underground pipe system in which a liquid heat transfer medium circulates.
There are different ways of distinguishing between the various geothermal fields attributed to deep geothermal energy. Criteria for the different deposits include the necessary drilling depth, the origin of the geothermal energy, the type of usage or the temperature level.