Working Principle of Thermal Power Plant - Advantages & Disadvantages

Principle of Thermal power plant : 

     The chemical energy of coal is converted into heat and then into steam by the boiler. The heat energy in steam is converted into mechanical energy by turbine. The mechanical energy or rotary energy of the turbine is converted into electrical energy by the generator.

Working Principle of Thermal Power Plant

Requirements for setting up of Thermal Power Plant :  

     The various requirements for setting up of a thermal power plant are :

1. Sufficient government land should be available or private land with reasonable price.

2. Coal should be available near the plant.

3. Sufficient quantity of water should be available.

4. Sufficient working personnel should be available in various loaders.

5. Facility for smoke and ash disposal should be available.

6. The site should be nearest to the coal mines so that transport cost of fuel is minimum.

7. The cost of the site should be reasonable.

8. The private land should be minimum. 

9. Large quantity of cooling ( for the condenser ) water should be available. 

10. Facilities should exist for the transport of fuel.

11. The site should be level and should not have any minerals, etc.

12. The site should allow strong foundation to the plant and building.

13. The land should not be rocky and marshy.

14. There should be ample area to develop the plant in future.

15. Accommodation for the operational and maintenance staff should be available nearby at reasonable rates.

16. Facility for the disposal of ash.

17. The chimney of the plant, do not obstruct the flying aeroplanes, i.e., the site should be away from the airport.

18. If the site is located near the centre, the distribution cost reduces.

19. The site should not be surrounded by residential building to avoid nusiance of smoke, noise etc.

20. If river water is used,the water should not be made dirty or polluted by fisheries.

Equipment of Thermal Power Plant :

1. Coal handling plant

2. Coal pulverisation plant

3. Steam Generator or Boiler

4. Ash handling

5. Steam Turbine

6. Condenser

7. Cooling towers and spray ponds

8. Feed water heater

9. Super heater

10. Economiser

11. Air preheater

12. A.C. Generator or Alternator

13. Exciter

14. Instrumentation.

Working of Thermal Power Plant :

     The coal is transported to the power house and is stored in coal storage plant. It is then delivered to the coal handling plant where it is crushed into small pieces also called pulverisation. The pulverised coal is then fed to the boiler through belt/chain conveyors.

     In the Boiler house the fuel is burnt and the water is converted into high pressure steam which is further superheated in a super heater. The super heated steam is passed through the turbine blades, thus the turbine converts the heat energy into mechanical energy. The pressure of the steam decreases and its volume increases, after imparting energy to the turbine rotor, it then, passes out of the turbine blades into the condenser. 

Working Principle of Thermal Power Plant

     In the condenser the cold water circulates with the help of a pump which condenses the low pressure wet steam. 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 then again heated in a high pressure heater where high pressure steam is used for heating. 

     The method of taking out steam from the turbines for feed water heating is called bleeding of turbines which increases the overall efficiency of the boiler. A large quantity of cooling water is required to condense the steam in the condenser. 

     The cooling water may be taken from the upper side of the river and after passing through the condenser it may be discharged to the lower side of the river. Such a system of cooling water is practicable if adequate quantity of water is available throughout the year. Where adequate quantity is not available water coming out from the condenser may be cooled in a cooling tower.

     The steam turbine is connected ( coupled ) to the alternator. The alternator converts the rotating/mechanical energy of turbine into electrical energy. The electrical output from the alternator is delivered to the busbars through transformers (step-up) and circuit breaker.

Advantages of Thermal Power Plant  :

1. Power generated is large.

2. Power stations can be located near the load centres.

3. Low calorific value fuels like coal, Lignite etc. can be used.

4. Initial cost is less compared to hydro and nuclear power stations.

5. Requires less transmission and distribution cost.

6.  It required less quantity of water as compared to hydra stations.

7. Long summer will not affect the power generation like hydro power.

Disadvantages of Thermal Power Plant  :

1. Air and water pollution takes place.  

2. Maintenance cost is more.

3.Takes time to generate steam and hence electrical power.

4. Needs more skilled persons.

5. Cost of the land is more.

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