The Geothermie, or terrestrial heat, is the warmth stored in the upper (accessible) part of the earth's crust. It covers the energy, as far as it can be extracted and used, stored in the earth, and ranks among the regenerativ energies. It can be used both directly, approximately for heating and cooling in the heating market, and for the production by electric current or in a force heat coupling. Geothermie designates both the engineering occupation with the terrestrial heat and its use, and the scientific investigation of the thermal situation of the earth body.

Origin of geothermal energy

Geothermie comes partially (estimated: 30-50 per cent) from the remainder warmth from the time of the earth emergence (Akkretion), on the other hand (estimated: 50-70 per cent) from radioactive decay processes, which produced warmth in the earth's crust for millions of years continuously and today to still produce. Completely near the surface portions from the sun exposure on the earth's surface and from the heat contact with air are added.

The temperature inside earth core amounts to according to different estimations 4500 "°C to 6500 "°C. 99 per cent of our planet are hotter than 1000 "°C; 99 per cent of the remainder are still hotter than 100 "°C. Nearly everywhere the soil in 1 kilometer of depth has a temperature of 35 "°C to 40 "°C (see also geothermal depth stage). Under special geological conditions - for example in today's or earlier volcanic areas - geothermal anomalies develop. Here the temperature can reach many hundred degrees Celsius.

Remainder warmth from the time of the earth emergence

The earth is before zirka 4.6 - 4.7 billion years by Akkretion of subject developed. Here the material heats up, whereby kinetic energy (kinetic energy) is converted into warmth. This heat energy kept because of the small heat conductivity of the rocks and thus the small heat emission to space until today partially and can be called remainder warmth from the time of the earth emergence.

Radioactive decay processes

This portion of the Geothermie e.g. decreases/goes back to the natural decay of the long-lived radioactive isotopes existing in the earth body like Uran-235 and U-238, Thorium-232 and Kalium-40. These elements are built, for example into the crystal lattices of certain minerals into the field-late and mica in granites. This concerns a natural form of the nuclear energy.

The achievement, which results from the radioactive decay, amounts to about 16 1012 Watts. With a middle Erdradius of 6,371 km the geothermal power density of the radioactive decay at the earth's surface amounts to about 0.032 Watts (32 mW) per square meter of earth's surface. This would constitute about half of the terrestischen heat flow.

Heat flow from the interior of the earth

The warmth is thus transported from deeper parts of the earth by thermal conduction, Konduktion, in addition, by convection into depths attainable for the use.

The terrestrial heat flow, those of the earth per square meter to space output, is about 0.063 Watt/m (63 mW/m (heat flow density). This is a relatively small value and refers to already on the fact that Geothermie is predominantly suitable for the decentralized use. In abnormal areas, as for instance volcanic areas, the heat flow can be larger around a multiple.

Because of the small heat flow density with the Geothermienutzung predominantly not the energy flowing from the interior of the earth, but the energy stored in the earth's crust is used or diminished. A Geothermienutzung must be dimensioned in such a way that cooling down the earth body concerned progresses so slowly that in the utilization period of the plant the temperature drops only to an extent, which permits an economical enterprise of the plant.

Organization of the Geothermiequellen

Geothermie can be used as energy source for the production of warmth and river. Here that becomes between the use

• Geothermie near the surface for direct use, usually to heating and cooling, and that
• deep Geothermie for direct use or also for generation of current differentiated.

Further between high and low enthalpy stores one differentiates. High enthalpy means that such stores place a high temperature ready.

Articles in category "Geothermie"

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