What
is Power Plant?
A power
plant or a power generating station,
is basically an industrial location that is utilized for the generation and
distribution of electric power in mass scale, usually in the order of
several 1000 Watts. These are generally located at the sub-urban regions or
several kilometers away from the cities or the load centers, because of its
requisites like huge land and water demand, along with several operating
constraints like the waste disposal etc. For this reason, a power generating
station has to not only take care of efficient generation but also the fact
that the power is transmitted efficiently over the entire distance. And that’s
why, the transformer switch yard to regulate transmission voltage also becomes an integral part of the power plant.
Types of Power Station
A power plant can be of several types depending
mainly on the type of fuel used. Since for the purpose of bulk power generation, only thermal,
nuclear and hydro power comes handy, therefore a power
generating station can be broadly classified in the 3 above mentioned types.
Let us have a look in these types
of power stations in
details.
Thermal Power Station
A
thermal power station or a coal fired thermal
power plant is by far, the most
conventional method of generating electric
power with reasonably high
efficiency. It uses coal as the primary fuel to boil the water available to superheated steam for driving the steam turbine. The steam turbine is then
mechanically coupled to an alternator rotor, the rotation of which results in
the generation of electric power. Generally in India, bituminous coal or brown
coal are used as fuel of boiler which has volatile content ranging from 8 to 33
% and ash content 5 to 16 %. To enhance the thermal efficiency of the plant,
the coal is used in the boiler in its pulverized form. In coal fired
thermal power plant, steam is obtained in very high pressure inside the steam boiler by burning the pulverized coal. This
steam is then super heated in the super heater to extreme high temperature.
This super heated steam is then allowed to enter into the turbine, as the
turbine blades are rotated by the pressure of the steam. The turbine is
mechanically coupled with alternator in a way that its rotor will rotate with
the rotation of turbine blades. After entering into the turbine, the steam
pressure suddenly falls leading to corresponding increase in the steam volume.
After having imparted energy into the turbine rotors, the steam is made to pass
out of the turbine blades into the steam
condenser of turbine. In the condenser, cold water at ambient temperature is
circulated with the help of pump which leads to the condensation of the low
pressure wet steam. Then this condensed water is further supplied to low
pressure water heater where the low pressure steam increases the temperature of
this feed water, it is again heated in high pressure. This outlines the basic
working methodology of a thermal power plant.
Nuclear Power Station
The
nuclear power generating stations are similar to the thermal stations in more
ways than one. However, the exception here is that, radioactive elements like
uranium and thorium are used as the primary fuel in place of coal. Also in a
nuclear station the furnace and the boiler are replaced by the nuclear reactor and the heat exchanger tubes. For the
process of nuclear power generation, the radioactive fuels are made to undergo
fission reaction within the nuclear reactors. The fission reaction, propagates
like a controlled chain reaction and is accompanied by unprecedented amount of
energy produced, which is manifested in the form of heat. This heat is then
transferred to the water present in the heat exchanger tubes. As a result,
super-heated steam at very high temperature is produced. Once the process of
steam formation is accomplished, the remaining process is exactly similar to a
thermal power plant, as this steam will further drive the turbine blades to
generate electricity.
Hydro-Electric Power Station
In
Hydro-electric plants the energy of the falling water is utilized to drive the
turbine which in turn runs the generator to produce electricity. Rain falling
upon the earth’s surface has potential energy relative to the oceans towards
which it flows. This energy is converted to shaft work where the water falls
through an appreciable vertical distance. The hydraulic power is therefore a
naturally available renewable energy given by the eqn: P = gρ QH Where, g =
acceleration due to gravity = 9.81 m/sec 2 ρ = density of water = 1000 kg/m 3 H = height of fall of water. This
power is utilized for rotating the alternator shaft, to convert it to
equivalent electrical energy. An important point to be noted is that, the
hydro-electric plants are of much lower capacity compared to their thermal or
nuclear counterpart. For this reason hydro plants are generally used in
scheduling with thermal stations, to serve the load during peak hours. They in
a way assist the thermal or the nuclear plant to deliver power efficiently
during periods of peak hours.
Diesel Power Station
For
generating electrical power, it is essential to rotate the rotor of
an alternator by means of a prime mover. The prime mover can be
driven by different methods. Using diesel engine as prime mover is one of the
popular methods of generating power. When prime mover of the alternators is
diesel engine, the power station is called diesel power station. The mechanical power required for driving
alternator comes from combustion of diesel. As the diesel costs high, this type
of power station is not suitable for producing power in large scale in our
country. But for small scale production of electric power, and where,
there is no other easily available alternatives of producing electric power,
diesel power station are used. Steam power stations and hydro
power plants are mainly used to produce maximum portion of the electrical
load demands. But for steam power station, sufficient supply of coal and water
are required.
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