Generating Electricity in a Thermal Power Station
A
thermal power plant is a power station which converts heat energy in to
electrical energy. The heat energy is produced from other primary sources.
Example of such primary sources which we term the “fuel” include: Coal, natural
gas, oil, etc.
Structure of a thermal power plant
The
schematic below is a simplified view of a thermal power plant made for easy
understanding. We shall study the role of the different compartments and how
they work together in order to produce electrical energy.
Role of the different parts of a thermal power plant
Fuel
(for
example coal, Natural gas, Oil): this is the primary source of energy
for example coal may be used. Hence by convention, we can term the
thermal power plant a coal thermal power plant. etc. Note that the
energy in fuel is chemical energy.
Combustor:
from the term combustion which means burn. So, this is the area where the fuel
is burnt to produce heat. So at this compartment, we obtain heat energy from
the chemical energy.
Boiler:
this
is the area where the heat produced is used to heat a medium into steam for
example, water into steam.
Pressurizer:
this
is where the steam produced in the boiler is pressurized (high pressure).
Turbine:
the
types of turbines used here are mostly steam turbines or gas
turbines. A steam or gas turbine is a mechanical structure design to rotate
when pressurized steam or gas passes through it. The turbine incorporated are
high pressure steam or gas turbines and or low-pressure steam or gas turbines.
So, both high and low-pressure turbines can be incorporated for output
maximisation and efficiency.
Condenser:
condenses
steam back into water. This is the area where the steam after passing through
the turbine, and has lost its most of its energy to drive the turbine is
condensed back into the water and sent back into the boiler. Hence a feedback
system.
Generator
(Alternator): is used to convert the mechanical energy
produced by the rotating turbine’s wheel into electrical energy.
Transformer:
step up transformers are mostly used to step up the voltage produced by the
generator at same frequency before it is transmitted/distributed.
Fans
and pumps: fans are used to blow in air (oxygen) for example in
the combustor needed for combustion of the fuel. Pumps are also used for
example in the pressurizer to pump the steam into the turbine. They are also
used in the condenser to pump back the water into the boiler.
Stack:
is
a compartment for ejection of flue gases.
Operating principle of a thermal power plant
Haven
known the operation of the different parts, below is a summary on the operation
of a thermal power plant.
The
fuel and air is injected into the combustor is burnt which produces heat. This
heat is used to heat water into steam in the boiler. The steam produced in the
boiler is pressurised and is used to rotate a steam turbines wheel which is
mechanically coupled to the rotor of a generator. As the rotor of the generator
rotates, this produces electrical energy.
A step-up transformer is now used to step up the voltage for transmission. Note that as the steam passes through the turbine it comes out at low pressure and enters the condenser which condenses the steam into water and is sent back into the boiler.
A step-up transformer is now used to step up the voltage for transmission. Note that as the steam passes through the turbine it comes out at low pressure and enters the condenser which condenses the steam into water and is sent back into the boiler.
Merits of a thermal power plant
- Requires less space compared to hydroelectric power plants.
- Low Cost of initial instalment compared to hydroelectric power plants.
- Can easily be installed anywhere
- Easy maintenance
Demerits of a thermal power plant
- Cause pollution since flue gasses are released to the atmosphere.
- High operating cost due to high cost of fuel.
