Geothermal Power Production:
Steam extracted from the well is cleaned in centrifugal separator which removes solid matters. The cleaned steam is then supplied directly into the steam turbine and the exhaust steam from the steam turbine is wet steam (i.e a mixture of water and steam) which passes through the condenser. The condenser condenses wet steam into water (through a cooling tower)
There are two ways of electric power production from geothermal energy
1. Heat energy is transferred to a working fluid which operates the power cycle. this may be particularly useful at places of fresh volcanic activity where the molten interior mass of earth vents to the surface through fissures and substantially high temperatures such as between 450 to 550 degree centigrade can be found.
2. The hot geothermal water and/or steam is used to operate the turbines directly from the wellhead the steam is transmitted by pipelines up to 1 meter in diameter over distances up to about 3 km to the power station. water separators are usually employed to separate moisture and solid particles from steam.
Geothermal plants are of following types
1. Vapour dominated (or) dry steam fields
Steam extracted from the well is cleaned in centrifugal separator which removes solid matters. The cleaned steam is then supplied directly into the steam turbine and the exhaust steam from the steam turbine is wet steam (i.e a mixture of water and steam) which passes through the condenser. The condenser condenses wet steam into water (through a cooling tower)
2. Liquid dominated high temperature systems
a) the flash steam open system
b) the binary cycle system
In flash steam open system hot brine from the reservoir reaches the wellhead at lower pressure by throttling process. the flash chambers brine separators which improves the quality of mixture. now steam is separated as a dry saturated steam and supplied to the steam turbine which produces electric power through a generator.
In flash steam open system hot brine from the reservoir reaches the wellhead at lower pressure by throttling process. the flash chambers brine separators which improves the quality of mixture. now steam is separated as a dry saturated steam and supplied to the steam turbine which produces electric power through a generator.
In binary cycle system the steam turbine is isolated from corrosive or non corrosive material and/or to accommodate higher concentration of non condensable gases. this is basically a rankine cycle with an organic working fluid.
3. Total flow concept system
in such a system both kinetic energy and heat energy of the steam fluid mixture, produced by flashing the geothermal brine are utilized. the overall efficiency for conversion in to electrical energy should be greater than other methods in which only the heat content of the brine is utilized. the hot brine from geothermal well is throttled where it becomes a two phase mixture of low quality. the two phases at this point are not separated and the full flow is expanded in the mixed phase expander which is coupled to the generator. the mixture from this expander/turbine is discharged in to condenser, then the brine condensate is re injected in to the well.
