ABSTRACT
Geothermal energy comes from the heat present inside the earth at considerable depths, which can reach temperatures of several thousand degrees. This endogenous energy comes from the heat initially contained in the planet, and generated by the decay of radioactive isotopes of elements, such as uranium, thorium and potassium in the earth’s crust.
A geothermal system essentially consists of three main elements: a heat source, a reservoir and a fluid, which is the carrier of heat transfer. The geothermal fluid is water, in the majority of cases meteoric water, in the liquid or vapour phase, depending on its temperature and pressure.
Hydrothermal systems, the only ones currently industrially explored, consist of geothermal reservoirs that contain water in both liquid and vapor phase, covered by impermeable rocks. They can be distinguished in “dominant water systems” and in “vapor-dominated systems”, depending on the status of fluid.
The first part analyzes the geothermal potential in terms of power generation and the effective exploitation carried out in the world.
The second part the technologies relating the different source typologies are described in terms of process modeling and performance optimization.
Finally, the emissions of geothermal plants are evaluated with reference to different sources and technologies and analyzed with respect to us impact on pollution and greenhouse effect.
