9 Utilisation of Ambient Air and Shallow Geothermal Energy
1,000 100 Energy of ambient air
Height in m
A typical characteristic of ambient air and near-surface heat it is the very low temperature level. The heat is mainly generated by solar radiation (Chapter 2). Only a small part of the energy in the soil (i.e. shallow geothermal energy) is not produced by the sun, but by the geothermal energy flow caused by the heat potential available within the earth (i.e. deep geothermal energy). The share of geothermal energy normally increases proportionally with an increasing depth underneath the surface of the earth (Chapter 2). Nevertheless, this type of energy is defined as geothermal energy –– independent of the origin of energy in the nearsurface ground (i.e. whether or not it results from solar radiation and/or geothermal energy stored in the deep underground, Chapter 2) (Fig. 9.1).
Solar radiation
10 Atmosphere
1
Water above surface
Shallow geothermal heat
Influenced by solar radiation
-1 -10
Soil with groundwater
-100 -1,000 Deep geothermal -10,000 heat
Depth in m
Geothermal energy resp. geothermal heat
Surface of the earth
Geothermal heat
Fig. 9.1 Terminology definitions
In line with this terminology it has been agreed that utilisation of geothermal energy in general, and shallow geothermal energy in particular, starts at the surface of the earth (Fig. 9.1). The difference between the use of shallow geothermal energy and of geothermal energy from deeper layers (Chapter 10) is arbitrary and goes back to an administrative regulation originally set up in Switzerland. Accord-