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Geothermal energy PDF Print E-mail
Geothermal energy is a form of energy obtained from the heat inside the soil. Hot water and steam, trapped in areas with volcanic and tectonic activity, are used for heating homes and producing electricity. It is a form of renewable energy.

Types of geothermal powerplants

There are three types of geothermic powerplants that are being used at this time on Earth to convert the geotermic water power into exectricity: 'dry', 'flash' and 'binary', depending on the fluid state: vapor or liquid, or by it’s temperature. ‘Dry’ powerplants were the first types of plants built, they used steam from geothermal springs. ‘Flash’ powerplants is the most popular powerplant today. They use water at the temperatures of 182 ° C, by injecting it at high pressure into the equipment at the surface. Binary cycle powerplants differ from the first two, because water or steam from geothermal spring does not come in contact with the turbine and electric generator. The water used reaches temperatures up to 200 ° C.
A power source with constant temperature, which contains heat in a virtually unlimited quantity available anywhere on the earth, is the energy of the soil.


Subsoil, from a certain depth has a temperature that is not influenced by seasonal variations. From the center of the earth there is a heat flux to the surface which leads to a medium temperature gradient of 1 º C at 33m. Given the small diffusability of the soil and large volume of soil involved in the process of “extracting the heat” we can consider that this energy resource can provide any quantity of heat necessary to heat homes.

The extraction of heat from the soil is called GEOEXCHANGE.


There are shown schematically the two circuits of the system with GeoExchange heat pump. This extract sheat from the external circuit of the building and delivers it at a higher temperature, into the internal circuit of the building, used to house heating.
The functionig of the heat pump is reversible so that, during the hot season it may be used to extract heat from the house (cooling) and introduce it into the soil.

Various systems of extraction of the heat from the soil