Geothermal power stations
/ GEOTHERMAL ENERGY AND ELECTRICITY PRODUCTION /
Currently, geothermal power stations produce electricity by using the fluids which escape from reservoirs underground. These are between 110°C and 350°C and can produce a flow of tens or hundreds of tonnes per hour, enough to produce a significant amount of electricity.
- Dry steam or wet steam condensing power stations
- The power stations use the Organic Rankine Cycle (ORC) principle or binary fluid technology.
- the geothermal fluid, once extracted, is brought to a heat exchanger. Here, it transfers some of its energy to an organic fluid, which then evaporates.
- For an identical pressure, this type of fluid has the particularity of vapourising at lower temperatures.
- The vapour produced is then released into a turbine, then condensed upon contact with the condenser’s water cooling circuit.
- Thus obtained, the liquid is then sent back to the exchanger using a pump. In this way, the cycle repeats: vapourisation, release, condensation, pressurisation.
- The working fluid (organic fluid) is retained in a completely closed circuit. As for the geothermal fluid, it is reinjected into the underground reservoir. This type of power station is single-unit and modestly sized (only a few units or tens of MWe).
Instead of cooling the fluid in a cooling tower, the heat is recovered and reprocessed for a range of applications. This is how electricity and heat can be produced at the same time.
- the working liquid is cooled by minimising the size of the cooling system
- the residual heat is used for activities which require this energy