electricity generation using thermal energy 2

8/3/2019 Electricity Generation Using Thermal Energy 2

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An important commodity Key for Development As the world's population grows, the need for

electricity will grow. World consumption of electricity is actually

expected to double over the next 30 years!



Easily transported Losses are minimum

Easily sub-divided Economical in use Easily converted into other forms of energy Easily controlled and regulated to suit the

requirement.



Nuclear fission The burning of fossil fuels (coal, natural gas, or

petroleum). Biomass Solar thermal energy (the sun as the heat source):

solar parabolic troughs and solar power towers

Geothermal power Ocean thermal energy conversion (OTEC )



Fossil fuels were produced from fossilization of carbohydrates.

The stored carbohydrates from dead plants, under

pressure and heat in the absence of oxygen,converted into Hydrocarbon compounds. General chemical formula – CnHm

The three general classes of fossil fuels are

Coal Oil

Natural gas



The most abundant fossil fuel in the world. Thought to be fossilized vegetation. The four major divisions, starting from oldest,

Anthracitic coals Bituminous coals

Sub bituminous coals

Lignite coals

As aging process increases, Coal gets harder – thehydrogen and oxygen fractions decreases, and thecarbon fraction increases.



Thought to be partially decomposed marinelife.

It is found in large domes of porous rocks. Three technologies are used to convert oil

into electricity:

Conventional steam

Combustion turbine

Combined-cycle technology



Natural gases are usually trapped beneathlimestone casings above petroleum reserves.

Composed of Methane plus smaller fraction of

other gases. There are two types-

that produced from decay of organic matters, and

that which has been trapped deep in earth’s crust since theearth was formed



In a thermal power plant, the chemicalenergy stored in fossil fuels such as coal,fuel oil, natural gas is converted

successively into thermal energy,mechanical energy and finally electricalenergy for continuous use and distribution

across a wide geographic area.



Rankine cycle based steam power plantsare the major source of power generation.

In the Rankine cycle, high pressure andhigh temperature steam raised in a boiler isexpanded through a steam turbine thatdrives an electric generator.



Coal conveyor : This is a belt type of arrangement.With this coal is transported

from coal storage place in power plant to theplace near by boiler.

Stoker : The coal which is brought near byboiler has to put in boiler furnance forcombustion.This stoker is a mechanicaldevice for feeding coal to a furnace.



Pulverizer : A pulverizer is a device for

grinding coal for combustion in a furnace in apower plant. The coal is put in the boiler afterpulverization.



Air Preheater : As the combustion flue gas exits

the boiler it is routed through a rotating flat basketof metal mesh which picks up heat and returns it toincoming fresh air as the basket rotates, This is

called the air preheater.



Flue gas & Fly Ash: Flue gas :

▪ The flue gas contains nitrogen along with combustionproducts carbon dioxide, sulfur dioxide, and nitrogenoxides.

▪ The sulphur and nitrogen oxide pollutants are removedby stack gas scrubbers which use a pulverized limestone

or other alkaline wet slurry to remove those pollutantsfrom the exit stack gas.



Fly Ash:

▪ The gas exiting the boiler is laden with fly ash, which aretiny spherical ash particles.

▪ The fly ash is removed by fabric bag filters orelectrostatic precipitators.

▪ Once removed, the fly ash byproduct can sometimes beused in the manufacturing of concrete.



The feed water used in the steam boiler is ameans of transferring heat energy from theburning fuel to the mechanical energy of thespinning steam turbine.

The total feed water consists of recirculated

condensate water and purified makeupwater.



Because the metallic materials it contacts are

subject to corrosion at high temperatures andpressures, the makeup water is highlypurified before use.



Boiler is an enclosed vessel in which water isheated and circulated until the water is

turned into steam at the required pressure.

This steam at the required pressure andtemperature is used to convert thermalenergy to mechanical work, which in turnmay be converted to electrical energy.



Condenser :

Steam after rotating steam turbine comes to

condenser. These condensers are heat exchangers which

convert steam from its gaseous to its liquid state,also known as phase transition.



Cooling Towers :

It is a tower- or building-like device in which

atmospheric air (the heat receiver) circulates indirect or indirect contact with warmer water (theheat source) and the water is thereby cooled.

Water, acting as the heat-transfer fluid, gives up

heat to atmospheric air, and thus cooled, isrecirculated through the system, affordingeconomical operation of the process.



Steam turbine is one of the most importantprime mover for generating electricity.

The principle of operation of steam turbine isentirely different from the steam engine.

The steam turbine depends completely uponthe dynamic action of the steam.



According to Newton’s Second Law of Motion,the force is proportional to the rate of change of momentum (mass × velocity).

If the rate of change of momentum is caused inthe steam by allowing a high velocity jet of steam to pass over curved blade, the steam will

impart a force to the blade attached on a rotorwhich is mounted on a shaft supported onbearings.

This constitutes the driving force of the turbine.



It is an electromechanical device thatconverts mechanical energy to alternating

current electrical energy. The generator, contains a stationary stator

and a spinning rotor, each containing miles of heavy copper conductor.

The electricity flows to a distribution yardwhere transformers increase the voltage fortransmission to its destination.



Transfers electric energy from one alternating-current circuit to one or more other circuits,either stepping up or stepping down the

voltage.

Here, the voltage from electric generators are

raised so that electric power can be transmittedover long distances.

Transformers act through electromagnetic

induction.



Feed Water and Steam Circuit

Coal and Ash Circuit

Air and Gas Circuit

Cooling Water Circuit



Fuel stored and fed to the boiler throughconveyor belts. Broken down into proper

shape for complete burning. Ash thus generated after burning is removed

from the boiler through ash handlingequipment



The total feed water consists of recirculatedcondensate water and purified makeup water.

The feed water cycle begins with condensate waterbeing pumped out of the condenser after travelingthrough the steam turbines.

Boiler feed pump, pumps out the recirculatedcondensate water and purified makeup water andfeeds it into the boiler drum where it is heated toform steam.



Wet steam is again heated in super heater before

passing through the turbine

Steam is expanded in the turbine to run it. Afterwhich again it goes to boiler for reheating

Some part of steam and water is lost while passingthrough different parts.



Air is required for combustion of fuel and issupplied through fans

Air is passed through air preheater to extractenergy from flue gases for proper burning of the fuel

Flue gases have ash and several gases whichare passed through the precipitator (dustcollector) and go to atmosphere throughchimney.



To condensate the steam, large quantity of cooling water is required which is taken from

river or pondage After passing through the condenser, it is fed

back to the river or Pondage

electricity generation using thermal energy 2

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