In places where the earth's crust is thin superheated geothermal fluid escapes
to the surface through fissures in the rock. Geothermal generation converts the
heat of naturally occurring steam and hot water into electricity. Everyone who has
seen the clouds of steam at Rotokawa or Mokai north of Taupo will be familiar with
this unique source of renewable energy.
For more facts on geothermal generation,
click here.
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 1.
Production Well
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The hot geothermal fluid is drawn up from between 2-3km beneath the surface.
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2.
Seperator
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Thermal fluid is separated into steam and hot water (known as brine)
and is used to spin a sequence of turbines connected to electricity generators.
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3.
Main Turbine
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High pressure steam (26 bar) is used to power the main electricity-producing
back pressure turbine. The turbines spin converting the kinetic energy of
the steam into mechanical energy.
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4.
Generator
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The turbine is connected via a shaft to magnets which in turn spin round
the inside the coils of the conductor. Here the mechanical energy is turned
into electrical energy ready for distribution and use via a power network.
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5.
Vaporiser
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The low pressure exhaust steam is then used to vaporise liquid pentane,
a hydrocarbon with a boiling point of 34°C, to produce a gas which is used
to drive the secondary (binary) turbines.
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6.
Binary Turbine
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Vaporised pentane is used to power the main electricity-producing back
pressure turbine. The turbines spin converting the kinetic energy of the
steam into mechanical energy.
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7.
Air Condenser
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The pentane gas is cooled in condensers and the pentane returned to start
the cycle again.
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8.
Vaporiser
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The low pressure exhaust steam is then used to vaporise liquid pentane,
a hydrocarbon with a boiling point of 34°C, to produce a gas which is used
to drive the secondary (binary) turbines.
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9.
Re-injection Well
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All post-production geothermal fluid (condensed steam and brine), is
then re-injected into the ground through purpose-built wells.
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