Dry steam type geothermal power plants form one of the main three types of geothermal power station that are in commercial operation today; the others two types of plants being the binary type and flash type. Geothermal power plant types are classed as renewable forms of energy and belong to the ‘green’ energy sector.
Dry steam geothermal resources are rare and only available in Italy and California (the geysers). As this type of geothermal resource is rare, there is less potential for wider utilization compared to the other two types of plants. Dry steam plants are more efficient than the other two types of plant because they do not need to pump large volumes of geofluid.
Steam (geofluid) is extracted from an underground vapour dominated reservoir. Steam rises to the surface through the production well and production well head valve.
A rock catcher is installed to separate foreign material from the process stream. The steam may then pass through a cyclone separator in order to separate the heavier and lighter phases. The separated heavier phase (condensate) is usually returned to the underground reservoir.
The pre-treated steam is then used to drive a steam turbine and a generator that is connected on a common shaft. After the turbine, there are a series of options.
- The geofluid is dumped to atmosphere.
- The geofluid is dumped to a water body (river or ocean).
- The geofluid is pumped back into the underground reservoir.
For various reasons, both environmental and economical, the geofluid is almost always returned to the underground reservoir.
Cooling towers are used to cool the steam and condense it to condensate prior to it being returned to the reservoir.
This 3D model shows all major components associated with an idealised dry steam geothermal power station, these include:
- Vapour Dominated Reservoir
- Production Well
- Injection Well
- Steam Turbine
- AC Generator
- Cooling Tower