Steam power plants types, Components, Thermodynamic cycle,Advantages and Disadvantages

Steam power plants types, Components, Thermodynamic cycle, Advantages, and Disadvantages

Steam power plant

            In a steam power plant, steam power is used to rotate the prime mover of the electric generator.

 In this process, heat energy is converted into mechanical energy and then to electrical energy through the turbine- generator system.


 Heat energy may be obtained by the proper combustion of a commercial fuel (coal, gas, oil etc). 
  Water is used to generate steam, which readily conveyed through pipes in a boiler by burning fuel in a furnace. 
  Steam power plants are also called ‘thermal power plants’.

            The prime movers of the steam power plant may be operated either in non-condensing or condensing.

1.Non-condensing Steam power plants:

Non-condensing plants:- The steam is exhausted from the prime movers and is discharged at atmospheric pressure or at greater than atmospheric pressure.

2.Condensing Steam power plants

Condensing plants:-  The prime movers exhaust discharge steam in to a condenser in which the pressure is less than atmospheric and steam is converted to water (most common).

Ø  Used in countries, where high -head water is not available for power generation in hydroelectric power plants.

Ø  Thermal the efficiency of the plant depends upon the choice of the steam cycle.

Principal components:-

       Boiler, superheating, feed water heating, steam reheating, turbine, and generator.

Advantages:-

                    i. The fuel is very cheap.

                  ii. Less initial cost compared to other generating stations.

                iii. It can be installed at any place irrespective of the existence of the coal. Coal can be easily transported to the site.

                iv. Require less space compared to hydroelectric power plants.

                  v. Cost of generation is less than a diesel power station.

  Disadvantages:-

              i. Pollutes the atmosphere due to the production of a large amount of smoke and fumes.

          ii. It is costlier in running cost as compared to a hydroelectric power plant.

Steam power plants can be

· Thermal power plants

· Super thermal power plants. ( ≥ 500MW)

Thermodynamic the cycle of steam flow

First law of thermodynamics:-

·     This law relates to the energy equation in its various forms.

·     It states that, when a system executes a cyclic process, the algebraic sum of the work transfer is proportional to the algebraic sum of the heat transfer.

Or,

·     Energy can neither be created nor be destroyed.

Second law of thermodynamics:-

·     Used in dealing with entropy and loss relations.

·     It states that,

 (1) Heat cannot on its own, flow from a body at a lower temperature to a body at a higher temperature (Clausius).

 (2) It is impossible to construct a heat engine that performs one complete cycle, and delivers work, exchanging heat from a single source (Kelvin-Plank).

            Or,

·     It is impossible to build a heat engine that has 100% thermal efficiency.

      When heat is transferred to water, its enthalpy and physical state change.

 As heating takes place, the temperature of water rises and generally its density decreases. 

The vapor formed in this process is known as steam, which is a gaseous state but does not entirely follow the laws of a perfect gas.

 The temperature at which boiling or vaporization occurs is dependent upon the purity of water, and the absolute pressure exerted upon it.

 The Carnot cycle cannot be applied to the steam turbines as the compression phase do not exist in steam plants.

   A steam power plant basically works on the Rankine cycle with small deviations from the ideal Rankine cycle.