GEOTHERMAL POWER PLANT

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GEOTHERMALPOWER PLANT
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What is Geothermal Energy?
The term geothermal comes from the Greek geo
meaning earth and therme meaning heat thus
geothermal energy is energy derived from the
natural heat of the earth.. The earths
temperature varies widely, and geothermal energy
is usable for a wide range of temperatures from
room temperature to well over 300 F. For
commercial use, a geothermal reservoir capable of
providing hydrothermal (hot water and steam)
resources is necessary. Geothermal reservoirs are
generally classified as being either low
temperature (lt150 C) or high temperature (gt150
C). Generally speaking, the high temperature
reservoirs are the ones suitable for, commercial
production of electricity. Geothermal reservoirs
are found in geothermal systems which are
regionally localized geologic settings where the
earths naturally occurring heat flow is near
enough to the earths surface to bring steam or
hot water to the surface
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DRY STEAM

• Power plants using dry steam systems were the
  first type of geothermal power generation plants
  built. They use the steam from the geothermal
  reservoir as it comes from wells, and route it
  directly through turbine/generator units to
  produce electricity. An example of a dry steam
  generation operation is at the Geysers in
  northern California

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HOT WATER / FLASH STEAM

• Hot water geothermal reservoirs are the most
  common type. In a liquid-dominated reservoir, the
  hot water has not vaporized into steam because
  the reservoir is saturated with water and is
  under pressure. To generate electricity, the hot
  water is piped from geothermal wells to one or
  more separators where the pressure is lowered and
  the water flashes into steam. The steam then
  propels a turbine generator to produce
  electricity.

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Single and Double Flash
Based on Juli 2004 data 40 total geothermal on
the word. Range capacity 3 MW 90 MW
On the same geothermal fluid condition 15 20
more power output.
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Binary Cycle

• A binary cycle power plant is used when the water
  in a hot water reservoir is not hot enough to
  flash into steam. Instead, the lower-temperature
  hot water is used to heat a fluid that expands
  when warmed. The turbine is powered from the
  expanded, pressurized fluid. Afterwards, the
  fluid is cooled and recycled to be heated over
  and over again.

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Working Fluid
Fluid Formula Mollar mass Relative Exit Area
Ammonia NH3 17.03 1.0
Propane C3H8 44.09 1.9
i-Butane i-C4H10 58.12 4.9
n-Butane C4H10 58.12 6.3
i-Pentane i-C5H12 72.15 12.2
n-Pentane C5H12 72.15 14.6
Condition Turbine inlet temperature 400
K Condensing Temp 320 K
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Geothermal Energy and the Environment
Geothermal energy is a renewable energy source
that does little damage to the environment. Geothe
rmal steam and hot water do contain naturally
occurring traces of hydrogen sulfide (a gas that
smells like rotten eggs) and other gases and
chemicals that can be harmful in high
concentrations. Geothermal power plants use
"scrubber" systems to clean the air of hydrogen
sulfide and the other gases. Sometimes the gases
are converted into marketable products, such as
liquid fertilizer. Newer geothermal power plants
can even inject these gases back into the
geothermal wells. Geothermal power plants do not
burn fuels to generate electricity as do fossil
fuel plants. Geothermal power plants release less
than one to four percent of the amount of carbon
dioxide (C02) emitted by coal plants. Emissions
of sulfur compounds from motor vehicles and
fossil fuel plants are also major contributors to
acid rain. Geothermal power plants, on the other
hand, emit only about one to three percent of the
sulfur compounds that coal and oil-fired power
plants do. Well-designed binary cycle power
plants have no emissions at all. Geothermal power
plants are compatible with many environments.
They have been built in deserts, in the middle of
crops, and in mountain forests.
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Comparison between Geothermal Power Plant and
Coal-fired Thermal Power Plant 
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Plant and Unit size

• Geothermal

• Conventional Steam Power Plant

• Relatively smaller unit size (Max. 110MW) makes
  unit construction cost high (because of (1)
  availability of geothermal steam (2) difficulty
  of transportation to geothermal power plant
  located in mountainous area (3) limitation of
  turbine last blade length.).

• The size can be decided depending on power
  demand, availability of fuel, etc. Plant size
  and unit size are big (600 to 1,000MW) makes unit
  construction cost low.

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STEAM CONSUMPTION
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Steam Turbine Condenser

• Geothermal

• Conventional Steam Power Plant

• Because steam pressure is relatively low (Usually
  6 to10 bara, Max. 19 bara), size of the turbine
  is bigger compared to thermal power plants of the
  same capacity
• All stainless steel (316L) or stainless clad
  steel because of NCGs.

• High steam pressure (about 90 bara) makes size of
  steam turbine small
• Depend on available main cooling water.

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COOLING TOWER

• geothermal

• Conventional steam power plant

• Because geothermal power plants are usually
  located in mountainous area where sufficient
  cooling water is not available, cooling tower is
  mandatory.

• N/A Because most of thermal power plants are
  located at sea side for fuel transportation and
  cooling (sea) water, cooling tower is not
  necessary

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STEAM POWER PLANT GEO THERMAL
Reference Data Steam Flow (ton/Hr) Steam Flow (ton/Hr) 145 145 ( 40.28 kg/s)
Reference Data Output (kW) at 145t/h Output (kW) at 145t/h 34,179 20,000 1.71 times
Theorotical Calculation Turbine Inlet Steam Condition P1 (bara) 87.3 8
Theorotical Calculation Turbine Inlet Steam Condition T1 (deg C) 510 170
Theorotical Calculation Turbine Inlet Steam Condition h1 (kJ/kg) 3,415 2,767
Theorotical Calculation Turbine Inlet Steam Condition s1 (J/kg K) 6,709 6,660
Theorotical Calculation Turbine Outlet Steam Condition P2 (bara) 0.09 0.11
Theorotical Calculation Turbine Outlet Steam Condition T2 (deg C) 44 48
Theorotical Calculation Turbine Outlet Steam Condition s2 (J/kg K) 6,709 6,660
Theorotical Calculation Turbine Outlet Steam Condition X2 0.80 0.80
Theorotical Calculation Turbine Outlet Steam Condition h2 (kJ/kg) 2,112 2,120
Theorotical Calculation Theoretical heat drop ?h (kJ/kg) 1,302 647
Theorotical Calculation Theoretical output (kW) at 145t/h Theoretical output (kW) at 145t/h 52,457 26,067 2.01 times
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Comparison of Major Equipment / System
Equipment / System Thermal Geothermal
Fuel System Yes N/A
Boiler Yes N/A
Turbine Yes Yes
Condenser Yes Yes
Boiler Feed Water System Yes N/A
Cooling Tower N/A Yes
Gas Extraction System Small Big
Feed Water Treatment System Yes N/A
Flue Gas De-sulferization Equipment Yes (1) N/A
(2) Depend on Environmental Regulation
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Main Cooling Water System

• The main cooling system of the main condenser
  comprises
• the two main circulating pumps 50 ,
• the cooling tower,
• the piping and valves.

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Cooling Tower Parameters

• The cooling system of the geothermal plant
  comprises a cooling tower of natural draught or
  forced draught type whose function is to
  discharge to atmosphere the waste heat rejected
  at the condenser.
• Considering the flow range of water to be cooled
  (average 6,500 m3/h for 20 MW unit / 15,900 m3/h
  for 55 MW unit) a forced draught tower with air
  directed through the tower by means of a fan, is
  the most suitable type for this application.

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Auxiliary Cooling Water System

• The auxiliairy cooling water system shall
  comprise
• The primary auxiliary cooling water system,
• The secondary auxiliary cooling water system.
• Primary auxiliary cooling water system
• The primary auxiliary cooling water system is
  derived from the cooled water of the cooling
  tower and shall be designed
• To ensure steam condensation inside the two
  ejectors condensers,
• To ensure the heat dissipation of the
  secondary auxiliary cooling system.

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Secondary Auxiliary Cooling Water System

• The secondary auxiliary cooling water system is a
  closed circuit fed from the treated fresh water
  system ensuring cooling of the turbo-generator
  coolers through the two water/water exchangers.
• This system shall mainly include
• The two secondary auxiliary cooling pumps,
• The two water/water exchangers,
• A make up tank.
• The turbo-generator air-coolers,
• The generator air-coolers,
• The air compressors coolers (if compressed air
  system water cooled),
• Various small coolers,

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