Geothermal energy

The term "geothermal energy" refers to the energy contained in the earth in the form of heat.
It is a huge and inexhaustible energy reserve, with a geothermal gradient which increases by 3° C every 100m depth, that is 30° C per kilometer.

Depending on the temperature of the geothermal fluid, this source can be used for multiple purposes: power generation (120 ° C), remote heating (80-100 ° C), industrial uses (at least 150 ° C).
At lower temperatures, geothermal energy can also be used in aquaculture (maximum 38 ° C) and greenhouse cultivation (38-80 ° C).

Geothermal energy is particularly exploited in the U.S., New Zealand, Italy, Iceland, Mexico, Philippines, Indonesia and Japan.
Today geothermal energy in italy is particularly used in Tuscany and to a lesser extent, in Lazio.
In 2000, there were geothermal plants operating in 22 countries, with a total capacity of 8,000 MW and a power output of 50 TWh.
Its potential is much higher and someone believes it can reach 80,000 MW in the short term.
Geothermal reserves are equivalent to 12 billion tons oil, amounting to one tenth of world reserves.

In the long term, the use of hot dry rock (HDR and DHP) located in depth is expected to become an important resource.
In many countries, including USA, Japan, England, France, Germany, Belgium and Switzerland, they are considering to drill areas without any environmental repositories, where it is possible to create water wells, in order to warm the water thanks to the heat of the Earth.
Once heated, the water is used in thermal power plants.