99% of our planet is hotter than 1000 °C and of the rest, 99% is hotter than 100 °C. This amount of energy is inexhaustible by human standards and well suited for solving a large part of our energy problems.
Compared with the amount of energy the sun beams annually to our planet in the form of radiated heat, the Earth has saved several million times more energy. This heat is gradually transmitted out of the Earth to the Universe: our planet gives off the incredible power of 40 Terawatts (equivalent to 40,000 nuclear power plants) which rises from the Earth’s centre to the surface. This heat should be used.
Geothermal energy near the Earth’s surface
For heating a house obviously far less heat is needed. This can be provided by near-surface geothermal energy (at up to 400m depth). This energy does not come from the heat emitted by the Earth’s core, but from solar radiation (direct solar radiation, rain etc.). Its temperature of 0 to 12 °C is determined by depth and time of year. Therefore a power source is needed to increase the temperature – a heat pump.
The ground-coupled heat pump works on the same principle as a refrigerator. That which is considered “warm” in winter, is considered “cold” in the summer. Thus heat pump facilities can be used for cooling as well as for heating.
In Germany, the *VDI guideline (No. 4640) is applied for the planning, completion and operation of installations used for exploiting near-surface heat.
*(Verein Deutscher Ingenieure / Association of German Engineers)