Free POLYTECHNIC notes on the internet for the first time by PRONAB BARUAH
Explain thermal power station and what are the advantages and disadvantages of it ?
Ans.
A power generating plant which uses heat to produce electrical energy is called thermal power station. Such plants may burn different types of fuel to produce necessary thermal energy. If it uses coal to produce energy, then it is called coal-fired power station.
A thermal power station is a power plant in which fuel is burnt to produce heat energy & finally this heat energy is transformed into electricity. Heat produced by the combustion of coal produces steam in a boiler at elevated temperature & pressure. It is then passed through a steam turbine ( prime mover ), which drive the alternator and thus electricity is generated. After the steam passes through the turbine, it is condensed in a condenser and recycled to where it was heated ; this is known as RANKINE CYCLE .
Some of advantages and disadvantages of thermal power station are given………………
ADVANTAGES
(a) The fuel (coal) used is quite cheap.
(b) It can be installed at any place irrespective of the existence of coal. The coal can be transported to the site of the plant by rail or road.
(c) The cost of generation is less than that of diesel power plant.
(d) Less initial cost as compared to other generating plants.
(e) It requires less space as compared to the hydroelectric power station.
DISADVANTAGES
(a) It is costlier in running cost as compared to hydroelectric power plant.
(b) It pollutes the atmosphere due the production of large amount of smoke and fumes.
(c) The operating and maintenance cost are high.
What are the factors or points that should be taken into account while selecting a site for a steam power station?
Ans.
In order to achieve overall economy, the following points should be considered while selecting a site for a thermal power station.
(a) Availability of water : Thermal power plant uses water as working fluid which repeatedly evaporated and condensed.
Water is used in large volumes in a steam power plant for the following purposes………..
(i) In boiler to raise the steam,
(ii) For cooling purposes such as in condenser, cooling tower etc.,
(iii) As a carrying medium such as in disposal of ash and
(iv) For drinking purpose.
Thus for a 250 MW power station, cooling water required may be 62×106 litres per hour. Therefore such plant should be located at a bank of river or near a canal to ensure the continuous supply of water.
(b) Availability of raw material : Modern thermal power stations using coal & oil as fuel, require a large amount of fuel. A steam power station consumes a large quantity of coal, so it should be located as near as possible to the coal fields to save the transportation charges. Besides transportation charges a plant located away from the coal fields may face some problems like, there may be failure of transportation system, strike at the mines etc. For such reasons a considerable amount of coal ( at least 15 day supply ) must be stored at all power station.
(c) Land : Considerable area is required for a power station. The cost of the land should be reasonable (cheap). Bearing capacity of the land should be adequate so that heavy equipment could be installed. Staff colony, coal storage, ash disposal requires appropriate amount of land. If the site is far away from a big city then entirely new facilities such as marketing, dairies etc will have to be provided for the staff.
(d) Nearest to the load centre : To reduce the transmission cost the plant should be located near the load centre ( consumer ) in case of d.c. supply.
(e) Distance from populated area : A huge amount of coal is burnt in steam power station & therefore smokes and fumes pollutes the surrounding area. So the plant should be located at considerable distance from the populated area.
(f) Transportation facilities : Site to be located or selected for this type of power station should have adequate transportation facilities such as railway, road etc for man, materials & machines . 