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Geothermal. What is it?

Geothermal. What is it?

Geothermal energy is the discipline of Earth Sciences that studies the set of natural phenomena involved in the production and transfer of heat or thermal energy from within the Earth.

In a broad sense, the geothermal concept can also be extended to the study of other planets. Its principles are exploited at a technological level in the production of electricity and cogeneration through geothermal power plants from the associated geothermal energy.

The origin of earth's heat from a geothermal

The heat of the Earth's core was originally generated during the accretion of the developed planet thanks to the gravitational pull force. Subsequently, heat continued to be generated thanks to the natural processes of nuclear fission of elements such as uranium, thorium and potassium.

Earth's heat is transferred from the interior to the Earth's surface through the mantle of the Earth by convection produced by the movement of magma or deep water. This is the origin of most phenomena such as volcanic eruptions, and other associated geothermal phenomena and thus evident on the surface of the earth, such as thermal springs, geysers and fumaroles.

This natural heat can be exploited for energy, specifically called geothermal energy. The term geothermal is often used to indicate precisely the exploitation of geothermal energy.

The heat flow from inside the Earth is only 1 / 20,000 of the heat that the Earth receives from the sun.

Thermal gradient

Depending on the heat flow and thermal conductivity, which varies according to the type of soil or rock, a different thermal gradient is observed (temperature variation as a function of depth).

This gradient can vary from 1 ° C every 30 m from the surface part of the earth's crust to 1 ° C every 10-15 m from the seabed in the vicinity of the oceanic ridges. The geothermal gradient in turn is strongly influenced by the circulation of terrestrial internal fluids.

Measurement of temperature and thermal gradient

The measurement is carried out with the appropriate instruments that are dropped in the wells. Accurate temperature measurement is complex and is disturbed by heat due to drilling and the presence of liquids (water, moisture, air) may be present in the soil.

Accurate temperature measurement is the accuracy of which is a function of the machinery used and the purpose of the instrument research type.

Instruments for measuring temperature in geothermal wells

The thermometers used in geothermal investigations must have two important characteristics:

  • Speed, therefore, must quickly reach thermal equilibrium. To have speed, therefore, these thermometers, must have low thermal inertia.
  • Reading should be possible when standing outside the well.

Used thermometers â € <â €

  • Thermocouples (error of 3/100 degrees)
  • Resistance thermometers (1/100 degree error)
  • Oscillators (error less than 1/1000 degrees)
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Last review: December 15, 2017

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