Changes

Economically significant concentrations of geothermal energy occur now where high temperatures (40° to more than 380°C; 104° to more than 716°F) are found in [[Porosity|porous]] and [[Permeability|permeable]] rocks at shallow depths (less than 3000 m; about 10,000 ft). The geothermal energy is stored in both the solid rock and the water or steam-filling pores and [[fracture]]s. The steam or hot water are used mainly as the fuel for the operation of electricity-generating turbines or for space heating.

Economically significant concentrations of geothermal energy occur now where high temperatures (40° to more than 380°C; 104° to more than 716°F) are found in [[Porosity|porous]] and [[Permeability|permeable]] rocks at shallow depths (less than 3000 m; about 10,000 ft). The geothermal energy is stored in both the solid rock and the water or steam-filling pores and [[fracture]]s. The steam or hot water are used mainly as the fuel for the operation of electricity-generating turbines or for space heating.

[[file:St54Figure48.JPG|thumb|200px|World geothermal electricity generation.<ref name=Salvador_2005>Salvador, A., 2005, Energy-A historical perspective and 21st century forecast: AAPG Studies in Geology 54, 208 p.</ref>]]

[[file:St54Figure48.JPG|thumb|200px|World geothermal electricity generation.<ref name=Salvador_2005>Salvador, A., 2005, Energy—A historical perspective and 21st century forecast: [http://store.aapg.org/detail.aspx?id=ADD-732 AAPG Studies in Geology 54], 208 p.</ref>]]

There are, therefore, three main requirements for the commercial development of geothermal resources: shallow high temperatures, rocks with good permeability, and sufficient volumes of water.

There are, therefore, three main requirements for the commercial development of geothermal resources: shallow high temperatures, rocks with good permeability, and sufficient volumes of water.

** '''Remaining heat release''': 34 x 1012 J/sec. It comes from the [[mantle]] and the nucleus and is the heat remaining after the formation of the planet.  

** '''Remaining heat release''': 34 x 1012 J/sec. It comes from the [[mantle]] and the nucleus and is the heat remaining after the formation of the planet.  

** '''Radioactive heat release''': 8 x 1012 J/sec. It comes from the [[crust]] and is produced by the fission of radioactive isotopes.  

** '''Radioactive heat release''': 8 x 1012 J/sec. It comes from the [[crust]] and is produced by the fission of radioactive isotopes.  

[[File:Figure 1.png|center|frame|{{figure number|1|}}Remaining heat and radioactive heat<ref>[https://www.mpoweruk.com/geothermal_energy.htm Electropaedia</ref>.]]

[[File:Figure 1.png|center|frame|{{figure number|1|}}Remaining heat and radioactive heat<ref>[https://www.mpoweruk.com/geothermal_energy.htm Electropaedia]</ref>.]]

=== Igneous phenomena ===

=== Igneous phenomena ===

High temperature fields are found in areas of higher igneous activity. They are related to extremely high gradients, corresponding to global tectonic process. They occur in plate borders, cortical thin areas or hot spots. They need an igneous source, an aquifer, and a impermeable layer to keep up pressure. In many cases, there is surface evidence such as geysers and fumaroles.  

High temperature fields are found in areas of higher igneous activity. They are related to extremely high gradients, corresponding to global tectonic process. They occur in plate borders, cortical thin areas or hot spots. They need an igneous source, an aquifer, and a impermeable layer to keep up pressure. In many cases, there is surface evidence such as geysers and fumaroles.  

[[File: Simplified diagram of a geotermal power plant.png|frame|center|Simplified diagram of a geothermal power plant.<ref>[http://www.bgs.ac.uk/research/energy/geothermal/ British Geological Survey]</ref>]]

[[File: Simplified diagram of a geotermal power plant.png|frame|center|{{figure number|5}}Simplified diagram of a geothermal power plant.<ref>[http://www.bgs.ac.uk/research/energy/geothermal/ British Geological Survey]</ref>]]

===Hot dry rock deposits or geothermal stimulated systems ===

===Hot dry rock deposits or geothermal stimulated systems ===

A geothermal central works similarly to a thermic one; the only variation is the way to heat water. Water vapor at high temperatures (up to 600°C) is directed from the inside the earth to the central, allowing the evaporation of water present in different pipes surrounding the boiler. The water vapor reaches higher pressure, thus it is used to move a turbine connected to the generator .When the turbine turns, electricity is produced, which goes from the generator to the transformers. These increase the tension of electricity, to transport this energy along electrical network to home users. The refrigeration system allows to condenses the water vapor, so that can be used again.

A geothermal central works similarly to a thermic one; the only variation is the way to heat water. Water vapor at high temperatures (up to 600°C) is directed from the inside the earth to the central, allowing the evaporation of water present in different pipes surrounding the boiler. The water vapor reaches higher pressure, thus it is used to move a turbine connected to the generator .When the turbine turns, electricity is produced, which goes from the generator to the transformers. These increase the tension of electricity, to transport this energy along electrical network to home users. The refrigeration system allows to condenses the water vapor, so that can be used again.

[[File: Simplified diagram of a geotermal plant.png|frame|center|{{figure number|6|}}Simplified diagram of a geothermal plant [https://www.linkedin.com/pulse/smart-grid-energy-harvesting-martin-ma-mba-med-gdm-scpm-pmp Linkedin article].]]

[[File: Simplified diagram of a geotermal plant.png|frame|center|{{figure number|6|}}Simplified diagram of a geothermal plant.<ref>[https://www.linkedin.com/pulse/smart-grid-energy-harvesting-martin-ma-mba-med-gdm-scpm-pmp Linkedin article]</ref>]]

==Sources==

==Sources==