school energy&environment

Geothermoeletric plants

Geothermal electricity power plants can be of different types; “back pressure system” if the steam, after being exploited , is freed into the atmosphere; “condensing system”, if the utilized steam is condensed and newly injected into the subsoil, through an injection well. “Flash” power plants are installed in areas dominated by water and are equipped with separators that separate the steam sent to the turbine, from the water that is then eliminated.
Geothermal power plants exploit geothermal heat. The flow of steam that comes from the subsoil either freely or channelled in deep geologic wells, produces a force that moves the turbine. The mechanical energy of the turbine is transformed into electricity by alternators. In the geothermal systems dominated by steam, geothermal energy can be utilized to produce electric energy, by forwarding the steam through steam-pipes to a turbine that is connected to a generator that produces electric current. If the fluid does not reach a sufficiently high temperature, the hot water may be used for the production of heat, as for example in teleheating plants.
Besides the “Direct Steam” technology, there is also another called “Binary Cycle” in which the heat of the geothermal fluid is exchanged with another fluid that activates the turbines. The Binary Cycle is a choice that is technically suited when the energy value of the fluid is low (temperatures below 180°C), while the “Direct Stream” is the more efficient choice in the presence of higher temperature geothermal fluid.
With equal fluid characteristics, the “Direct Stream “ plant has significant advantages: the environmental impact is less, thanks to the lesser amount of fluid required to produce the same amount of energy (and therefore less wells to drill and less pipelines to be built), the structure is more compact and therefore occupies less territory, and is less noisy than the Binary Cycle technology due to the reduced number of cooling towers and related fans. Lastly, both technologies do not have significant differences in the emissions in the atmosphere, as, also in the Binary Cycle, the gases that are separated from the liquid phase are treated.