Thermal Power Station or
Stream Power Station
India has rich stocks of coal as a natural resource. Chemical energy stored within the coal is
finally transformed into Electrical energy through the process of these stations. Heat released by the
combustion of coal produces steam in a boiler at elevated temperatures and pressures. It is then
passed through steam turbines, which drive the alternator, the output of which is the electrical energy
shows a simple schematic diagram of a modern coal-fired thermal station.
In India, coal is generally of low grade containing ash upto 40 %.
It poses two problems.
(i) Calorific value is low and hence system efficiency can be increased only by additional processes
like pulverizing the coal and using oil firing to start with,
(ii) large volumes of ash have to be handled
after ensuring that ash is extracted to the maximum possible extent (upto 99 %) by using electrostatic
precipitators, before flue gases from boiler are finally passed on to the atmosphere.
Coal is burnt in the boiler. This heat converts water into steam when passed through the boiler
tubes. Modern plants have super heaters to raise the temperature and pressure of steam so that plant
efficiency is increased. Condenser and cooling tower deal with steam coming out of turbine. Here,
maximum heat is extracted from steam (which then takes the form of water) to pre-heat the incoming
water and also to recycle the water for its best utilization.
Steam-turbine receives controlled steam from boiler and converts its energy into mechanical
energy which drives the 3-ph a. c. generator (=alternator). The alternator delivers electrical energy, at
its rated voltage (which may be between 11 to 30 kV). Through a circuit breaker, the step up transformer
is supplied. Considering the bulk-power to be transmitted over long distances, the secondary rating
of this transformer may be 220 or 400 kV (as per figures for India). Through Extra-High Voltage
Switch gear, the Bus is energized and the EHV primary transmission line can transport power to the
Load centres connected to it.
A modern coal-fired thermal power station consumes about 10 % of its power for supplying to
the Auxiliaries. These are mainly as follows.
(a) Main-exciter for alternator.
(b) Water pumps.
(c) Fans: Forced draught and Induced draught fans for Pre-heaters and Chimney.
(d) Coal handling plant including pulverising mill.
(e) Ash handling plant including Electrolytic Precipitator.
Naturally, whenever such a station is to be brought into operation (either at commissioning or
after repairs/maintenance schedule) the power required for the auxiliaries has to be supplied by the
grid. Once the system is energized fully, it will look after supplying power to its own auxiliaries.
Merits of coal Based Plants :
1. Fuel (=coal) is cheap.
2. Less initial cost is required.
3. It requires less space.
4. As a combination of all above points, the cost of generating unit of electrical energy is less
Demirits Of Plant ;-
1. Atmospheric pollution is considerable.
2. Coal may have to be transported over long distances, in some cases, after some years, and then
the energy cost may be quite high.
Fell free to comment below if u have any doubts
Stream Power Station
India has rich stocks of coal as a natural resource. Chemical energy stored within the coal is
finally transformed into Electrical energy through the process of these stations. Heat released by the
combustion of coal produces steam in a boiler at elevated temperatures and pressures. It is then
passed through steam turbines, which drive the alternator, the output of which is the electrical energy
shows a simple schematic diagram of a modern coal-fired thermal station.
In India, coal is generally of low grade containing ash upto 40 %.
It poses two problems.
(i) Calorific value is low and hence system efficiency can be increased only by additional processes
like pulverizing the coal and using oil firing to start with,
(ii) large volumes of ash have to be handled
after ensuring that ash is extracted to the maximum possible extent (upto 99 %) by using electrostatic
precipitators, before flue gases from boiler are finally passed on to the atmosphere.
Coal is burnt in the boiler. This heat converts water into steam when passed through the boiler
tubes. Modern plants have super heaters to raise the temperature and pressure of steam so that plant
efficiency is increased. Condenser and cooling tower deal with steam coming out of turbine. Here,
maximum heat is extracted from steam (which then takes the form of water) to pre-heat the incoming
water and also to recycle the water for its best utilization.
Steam-turbine receives controlled steam from boiler and converts its energy into mechanical
energy which drives the 3-ph a. c. generator (=alternator). The alternator delivers electrical energy, at
its rated voltage (which may be between 11 to 30 kV). Through a circuit breaker, the step up transformer
is supplied. Considering the bulk-power to be transmitted over long distances, the secondary rating
 |
| thermal Power station Block diagram |
Switch gear, the Bus is energized and the EHV primary transmission line can transport power to the
Load centres connected to it.
A modern coal-fired thermal power station consumes about 10 % of its power for supplying to
the Auxiliaries. These are mainly as follows.
(a) Main-exciter for alternator.
(b) Water pumps.
(c) Fans: Forced draught and Induced draught fans for Pre-heaters and Chimney.
(d) Coal handling plant including pulverising mill.
(e) Ash handling plant including Electrolytic Precipitator.
Naturally, whenever such a station is to be brought into operation (either at commissioning or
after repairs/maintenance schedule) the power required for the auxiliaries has to be supplied by the
grid. Once the system is energized fully, it will look after supplying power to its own auxiliaries.
Merits of coal Based Plants :
1. Fuel (=coal) is cheap.
2. Less initial cost is required.
3. It requires less space.
4. As a combination of all above points, the cost of generating unit of electrical energy is less
Demirits Of Plant ;-
1. Atmospheric pollution is considerable.
2. Coal may have to be transported over long distances, in some cases, after some years, and then
the energy cost may be quite high.
Fell free to comment below if u have any doubts
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