Heat is produced between the crust and the upper level of the earth and is transferred to the surface by diffusion: convective movements in the magma (molten rock), and due to deep-water circulation. We can see the result of this activity on the surface in the form of volcanoes or geysers, among others.

In order to harness this energy, the crust has to be perforated at a depth of around 3,000 metres, although the largest heat reserves are found at 6,000 metres. This is where steam of high enough pressure to move a turbine or generate electric current is found.

The pioneers
Currently, 176 countries generate electric current using geothermic energy. It was in Tuscany where this process was pioneered in 1904. Geothermic fluids are also used for heating in Budapest (Hungary), in some parts of Paris (France), and in Reykjav�k (Iceland), in other Icelandic cities and in many parts of the U.S.

Geothermic plants are less efficient (12%) than coal plants (30%) or nuclear plants (33%), because the installations that transform geothermic energy into electricity use up three times more energy than coal plants. However, these plants are cheaper to run. For this reason, they continue to be used as an energy resource.

Advantages
Geothermic plants are designed to function 24 hours a day, the whole year round, given that power cuts caused by the weather, natural disasters or political occurrences that may interrupt the transport of fuels do not affect them.

Electricity generation using geothermic energy helps to conserve non-renewable fossil fuels and both prevents and reduces damaging emissions.

Did you know...?
-Between 1995 and 2002, installed geothermic energy increased continuously from 6,837 to 8,356 MW, a jump of 22.3%, according to EurObserv'ER.
-A volume of 520,000 cubic metres of underground rock at a temperature of several hundred degrees contains enough energy to cover the world's energy uses for a whole year.

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