Geothermal Power refers to power from the heat (thermal) of the
earth (Geo). The inside of the earth consists of the outer crust, the
mantle and the inner core. The topmost layer of the mantle just below the
earth crust contains molten rocks called magma. Magna is a high
temperature (estimated to be in the order of 1000 - 1400
oC) and highly viscous fluid.
Volcano results when magma breaks through the earth crust as lava ("river"
of magma) on the earth surface. Any surface water that trickles down the
cracks in the earth crust and comes in contact with magna (or molten
rocks) get heated up and have escaped to the surface as hot springs.
The temperature of the earth rocks increases as
it goes deeper down. There is 3oC
temperature increase for every 100 meters into the the earth and by the
depth of 3,000 m or 3 Km below the
ground, the rock would be hot enough to boil water.
Geothermal power harnesses this heat source
benefit the earth crust to provide heat (as in heated water) and
electricity to homes and industries. Geothermal power has been used in
several parts of the World (and most profoundly in Iceland) to provide
heating for swimming pools, domestic hot water at homes and industries and
building space heating. It has also been used to provide electricity. The
generation of electricity from geothermal energy source is carried out
through a Geothermal Power Plant.
Geothermal power plants
are similar to Coal powered plants and
hydroelectric powered plants and
Nuclear Plants in the way they
produce electricity. The difference in the systems is their fuel
sources.
Essentially, the technologies produce
the energy that drives the turbine and the electromagnetic
rotor which creates
flow of electrons (or electricity). Geothermal Power Plants obtain the fuel that
drives the plants from hot fluids buried several kilometres below
the earth surface.
Water from the surface (e.g. rain water)
seeping through the cracks on the earth surface,
over several years, fill the
underground reservoir.The fluid
(consisting of water
and dissolved materials and solids picked up as the water seeped down) in the
underground reservoir is heated up to very high temperatures
when it comes into contact with the
molten rock (magma) beneath the earth crust, to form the superheated
fluids. The superheated fluids do not
turn into steam while underground because they are not exposed to air. As
the fluid get to the surface, they become steam and could be used
similarly to the steam generated from coal fired plants, to power a
turbine that drives an electromagnetic system that generates electricity
for domestic and industrial uses.
An approach, called crystallizer-reactor clarifier technology,
described below, is used to turn the superheated fluids into steam while
removing solids from it. The fluid is used to drive the turbine that
generates electricity.
The components of a
geothermal power plant are as described below:
Production Wells: The superheated
fluids are tapped by production wells drilled up to
1500 to 3000 m (1.5 to 3.0 Km)
below the earth surface. Under its own pressure,
the superheated fluids flow through the
production wells to the surface. As the hot fluid
flows to the surface, the pressure lessens causing a small amount to
become steam.
Wellhead Separator: The mixture of
the hot fluid and and the steam moves through a surface pipeline
system to a
wellhead separator where the pressure is reduced. In the wellhead
separator most the remaining hot fluid
vaporises to produce high pressure steam.
Standard Pressure Crystallizer: Any
hot fluid not flashed as steam, up to this
point,
moves to a standard pressure crystallizer to produce standard pressure
steam.
Low
Pressure Crystallizer: Remaining
hot fluid is then flashed at a lower pressure,
inside a low pressure crystallizer, to create a lower
pressure steam.
All steam
(high, standard and low pressure) created is
sent to a turbine. The force of the steam spins
the turbine’s blades which turns the shaft connected to an electrical
generator. Electrical charge is created and can be directed to a
transformer where the voltage is increased and sent down power lines.
At the end of these processes, any
fluid not converted into steam is
returned to the underground reservoir where in time
they will be re-heated and re-used, making the process renewable.
