Geo Thermal Energy

Geothermal energy is the energy contained as heat in the Earth's interior. The origin of this heat is linked with the internal structure of our planet and the physical processes occurring there. Despite the fact that this heat is present in huge, practically inexhaustible quantities in the Earth's crust, not to mention the deeper parts of our planet, it is unevenly distributed, seldom concentrated, and often at depths too great to be exploited industrially.

The heat moves from the Earth's interior towards the surface where it dissipates, although this fact is generally not noticed. We are aware of its existence because the temperature of rocks increases with depth, proving that a geothermal gradient exists: this gradient averages 30°C/km of depth.

There are, however, areas of the Earth's crust which are accessible by drilling, and where the gradient is well above the average. This occurs when, not far from the surface (a few kilometres) there are magma bodies undergoing cooling, still in a fluid state or in the process of solidification, and releasing heat. In other areas, where magmatic activity does not exist, the heat accumulation is due to particular geological conditions of the crust such that the geothermal gradient reaches anomalously high values.

The extraction and utilisation of this large quantity of heat requires a carrier to transfer the heat toward accessible depths beneath the Earth's surface. Generally the heat is transferred from depth to sub-surface regions firstly by conduction and then by convection, with geothermal fluids acting as the carrier in this case. These fluids are essentially rainwater that has penetrated into the Earth's crust from the recharge areas, has been heated on contact with the hot rocks, and has accumulated in aquifers, occasionally at high pressures and temperatures (up to above 300°C). These aquifers (reservoirs) are the essential parts of ...