Thermal Engg. CHAPTER 1 Sources of Energy • Man has needed and used energy at an increasing rate for his sustenance. Energy utilization increases due to rapid growth in industrialization. Economic development of any country depends on the energy sources. • So energy is the primary and most universal measure of all kinds of work for human beings and nature and closely related with energy utilization. • Everything that happens in the world is the expression of flow of energy in one of its form. Classification of Various Sources of Energy Conventional OR Non Renewable Non Conventional OR Renewable Energy Sources Energy Sources 1. This source of energy can be pr oduced fro m 1. Th is so urce of energy can be produced from fos sil fuels such as coa l nat ura l gas pet roleum sun win dfal ling water sea waves etc. oiluranium etc. !. They a re exhaust ed and limit ed as they cannot !. They can never be exhausted and therefore be renewed. are renewable. ". Energy density is high. ". Energy density is low. #. $ost of generation high. They are very #. $ost of generation is low. They are less expensive to be maintainedstored and expensive due to local availability and easy transmi tt ed as they are carr ied over long to maintain. distances through transmission grid and lines. %. Th ey c au se p ol luti onwhe n us ed as they emit %. T he y are g ener al ly po ll ut io n fr ee. smoke and ash. Non Renewable Energy Sources Thermal Energy &uclear Energy 'ydraulic Energy Renewable Energy Sources Solar Energy (ind Energy )io Energy 'ydro Energy *eothermal Energy +cean Energy Or(ave and Tidal Energy Conventional OR Non Renewable Energy Sources FOSSIL FUELS • ,ossil ,uels consist of deposits of once living organisms. The organic matter takes centuries to form. • ,ossil ,uels principally consist of carbon and hydrogen bonds. 1
• Man has needed and used energy at an increasing rate for his sustenance. Energy
utilization increases due to rapid growth in industrialization. Economic development ofany country depends on the energy sources.
• So energy is the primary and most universal measure of all kinds of work for human
beings and nature and closely related with energy utilization.
• Everything that happens in the world is the expression of flow of energy in one of its
form.
Classification of Various Sources of EnergyConventional OR Non Renewable Non Conventional ORRenewable Energy Sources Energy Sources1. This source of energy can be produced from 1. This source of energy can be
produced from
fossil fuels such as coal natural gas petroleum sun wind falling water sea waves etc.
oil uranium etc.!. They are exhausted and limited as they cannot !. They can never be exhausted and
therefore be renewed. are renewable.". Energy density is high. ". Energy density is low.#. $ost of generation high. They are very #. $ost of generation is low. They are
lessexpensive to be maintained stored and expensive due to local availabilityand easytransmitted as they are carried over long to maintain.
distances through transmission grid and lines.%. They cause pollution when used as they emit %. They are generally pollution free.
smoke and ash.
Non Renewable Energy Sources
Thermal Energy
&uclear Energy
'ydraulic Energy
Renewable Energy Sources
Solar Energy
(ind Energy
)io Energy
'ydro Energy
*eothermal Energy
+cean Energy Or (ave and Tidal Energy
Conventional OR Non Renewable Energy SourcesFOSSIL FUELS
• ,ossil ,uels consist of deposits of once living organisms. The organic matter takes
centuries to form.• ,ossil ,uels principally consist of carbon and hydrogen bonds.
• There are three types of fossil fuels coal or solid fuel li-uid fuel or oil and gaseous fuel
or natural gas.
• ,ossil fuels are the main fuel for the thermal power.
• There is a fear that they will get exhausted eventually in the next centurary.
Solid Fuels:
• These are
&atural Solid ,uels eg. (ood peat coal / lignite anthrasite and bituminous coals0depending on the relative proportions of fixed carbon moisture and volatile matter.
rtificial Solid ,uels eg. (ood charcoal coke and pulverized coal etc.
Liquid Fuels:
• They are crude petroleum and various oily residues obtained in distilling petroleum
shale oil and coal tar.
• These fuels have more advantages over solid fuels.
• $rude oil is extracted from oil production wells drilled either on2shore or off shore.
• 3t is then refined in refineries to obtain petrol diesel kerosene furnace oil lubricating
oil paraffin asphalt tar etc.
• 3t consists of a mixture of gases li-uids and solid hydrocarbon with small amount of
nitrogen and sulphur compound.
Gaseous Fuels:
Advantages of Gaseous Fuels
• 3t can be produced at a central location and clean gas can be distributed over a wide
area.• &uisance of smoke production and ash disposal eliminated at point of fuel utilization.
• *reater control of variation in demand conditions of combustion and nature of flame
and heating atmosphere possible.
• *reater economy by use of efficient heat exchanger methods possible.
• *aseous fuels re-uire far less excess air for complete combustion.
isadvantages of Gaseous Fuels
• 4ower produced with gaseous fuels is less when compared to solid and li-uid fuels.
• s its specific volume is high gaseous fuel containers are much larger than those for
li-uid fuels. 'ence they are li-uefied by moderate compression at normal temperatureand stored in tank or cylinder.
Natural Gas
• 3t is the only gas occurring in nature.
• 3t contains 56 to 768 methane rest are propane butane heavier and more complex
hydrocarbons carbon dioxide nitrogen and some helium. lso methane is agreenhouse gas with a global warming potential approximately # times that of carbondioxide.
• 3t is stored as a super cooled 0cryogenic: li-uid.
• The temperature re-uired to condense 9&* depends on its precise composition but it is
typically between 21!6;$ and 21<6;$.
• The advantage of 9&* is that it offers an energy density comparable to petrol and diesel
fuels extending range and reducing refuelling fre-uency.
• The disadvantage is the high cost of cryogenic storage on vehicles and the ma=or
infrastructure re-uirement of 9&* dispensing stations production plants andtransportation facilities.
Co$%ressed Natural Gas "CNG#
• $&* is stored on the vehicle in high pressure tanks at !6 to !% M4a pressure 0!66 to
!%6 bar:.
• 3t is lighter than air and thus will normally dissipate in the case of a leak giving it a
significant safety advantage over gasoline or 94*.• s it does not li-uefy even under high pressure it has a lower energy density.
Li!uefied &etroleu$ Gas or Autogas "L&G#
• 3t is produced as a by product of natural gas processing and petroleum refining.
• 3t consists mainly of propane propylene butane and butylene in various mixtures.
• The components of 94* are gases at normal temperatures and pressures and hence it
can evaporate and therefore stored in pressurized steel bottles.
• 3t can vary widely in composition leading to variable engine performance and cold
starting performance.
• 94* is heavier than air and thus will flow along floors and tend to settle in low spotssuch as basements. Such accumulations can cause explosion hazards.
3n general the chemical energy of fuel is converted into heat energy by the combustion ofthe fuel. This heat energy produced is utilized for the production of mechanical energy which can be converted into electrical energy for many applications such as in
3nternal $ombustion 03$: Engines
$ooking purposes
To generate electricity in thermal power plant.
THERA! ENERG" SO#RCES $THERA! PO%ER P!ANT&• Steam is important working fluid which can be used for producing mechanical energy in
thermal power plant.
• Steam can be generated by using any type of fuel such as coal oil or gas. The type of
fuel used depends upon the availability of the fuel in a particular country.
'OR(ING OF )*ER+AL &O'ER &LAN)
• Steam is generated in the boiler of the thermal power plant using the heat of the fuel
burned in the combustion chamber.
• The steam generated is passed through steam turbine where part of its thermal energy
is converted into mechanical energy which is further used for generating electric power.
• The steam coming out of the steam turbine is condensed in the condenser and the
condensate is supplied back to the boiler with the help of the feed pump and the cycle isrepeated.
FUNC)ION
• )oiler / 3t is used to generate steam.
• $ondenser 2 3t is used to condense the steam coming out of steam turbine at low
pressure.
• Steam Turbine / 3T is used to convert part of heat energy of steam into mechanical
energy.
• ,eed 4ump / 3t is used to raise the pressure of the condensate from the condenser
pressure 06.61% bar: to boiler pressure 0!66 bar:.
• +ther $omponents Economiser Superheater and Steam ,eed 'eaters / Steam from
different points of turbine is fed to the heaters to heat the condensate to a highertemperature and to increase the overall efficiency of the thermal power plant.
A,AN)AGES OF )*ER+AL &O'ER &LAN) • The fuel used is -uite cheap.
• 9ess initial cost as compared to other generating plants.
• 3t can be installed at any place irrespective of the existence of coal.
• The coal is transported to the site of the plant by rail or road.
• 3t re-uires less space as compared to hydro power plants.
• $ost of generation is less than that of diesel power plants.
ISA,AN)AGES OF )*ER+AL &O'ER &LAN)
• 3t pollutes the atmosphere due to production of large amount of smoke and fumes.
• 3t is costlier in running cost as compared to hydroelectric plants.
• 3n nuclear reactor for reaction to occur it re-uires a very heavy elemental isotope
typically some form of uranium or plutonium and other a very light >free neutron?.
• The light particle collides with the heavy particle which splits into two or three pieces.This reaction is called fission.
• This fission produces a ton of energy in the form of both kinetic energy and
electromagnetic radiation.
• These new pieces includes two new nuclei 0 by products: some photons 0gamma rays:
but also some more free neutrons. These newly produced free neutrons zoom aroundand smack into more uranium or plutonium isotope which in turn produces more energyand more free neutrons and it keeps going as a nuclear fission chain reaction.
'OR(ING OF NUCLEAR &O'ER &LAN)
• 3n nuclear power plants the boiler of steam or thermal power plant is replaced by
nuclear reactor. The nuclear fission reaction heat is used either for steam generation orheating the working fluid.
• The heat in the nuclear reactor is used by steam turbine which is converted to
mechanical energy and it is further used for generating electric power.
• (ater from rivers can be used for condensing the steam in the condenser provided it is
available throughout the year.
• 3f not then a cooling tower is generally used.
• 3n this case the same is used again and again for condensing the steam.
• The warm water coming out of condenser after absorbing the heat of exhaust steam is
passed through the cooling tower where it is cooled in the current of air.
• This cold water is again passed through the condenser.
• The working cost of this system is less than other type of power generation system as
no fuel is used.
• 'ydro power is fuelled by water so it?s a clean fuel source. 3t does not pollute the air like
power plants that burn fossil fuels such as coal or natural gas.
• +nce a dam is constructed electricity can be produced at a constant rate.• 3t electricity is not needed the sluice gates can be shut stooping electricity generation.
• The lake?s water can be used for irrigation purposes.
ISA,AN)AGES OF *-RO &O'ER &LAN)
• The capital investment is generally high.
• 'ydro power plants can be impacted by draught. (hen water is not available the hydro
power plants cannot produce electricity.
• 'ydro power facilities impact the local environment and may compete with other uses
for the land. 'umans flora and fauna may lose their natural habitat.
SO!AR ENERG"
• Solar energy refers to the direct use of the energy contained in the sunlight.
• Solar energy is available as long as the sun shines but its intensity depends on weather
conditions and geographic location.
• The earth and its atmosphere receive continuously 1.<x161< ( of radiation from the sun.
• The surface receives about #<8 of the total solar energy that reaches the earth. +nly
this amount is usable.
• The density of sunlight falling on earth?s surface is considerably low and therefore it
cannot be used directly for power generation.
• $onverting the sun?s radiant energy to heat is the most common and well developedsolar conversion technology today.
*lazing2 one or more covers of transparent material like glass plastics etc.
bsorber2 a plate with tubes or passages attached to it for the passage of a working fluid.The absorber plate is usually painted black.
Tubes2 to facilitate the flow of heat transfer fluid.
3nsulation2 to minimize heat loss from the back and the sides.
$ontainer2 box or casing.
'OR(ING OF FLA) &LA)E COLLEC)OR• The solar radiation falls on absorber plate after coming through one or more transparent
glass covers. The absorbed radiation is partly transferred to a li-uid flowing through tube which is fixed to absorber plate. The remaining is lost by convection and radiation.
• The transparent cover helps in reducing the losses by convection and re2radiation while
thermal insulation on bottom and the side helps in reducing the conduction heat loss.
• The li-uid absorbs heat and decreases in density thus flowing to the top. s the water
heats up to <%;$ to 166;$ these collectors are used only for domestic purposes.
• The li-uid like ,reon can be used to generate power as it boils at lower temperatures.
The flat plate collectors can achieve a temperature of 1#6;$ with booster mirror.
Cylin*rical Parabolic Concentrating Collectors
'OR(ING OF C-LINRICAL &ARA.OLIC CONCEN)RA)ING COLLEC)OR
• They are typically used for temperatures above 166;$. it consists of a concentrator and
a receiver 0absorber:.
• The concentrator is a mirror reflector having the shape of a cylindrical parabola. The sun
rays incident on concentrator are focused on axis where it is absorbed on the surface ofabsorber tube or receiver and transferred to the fluid flowing through it.
• The absorber tube is a concentric glass cover which helps in reducing convective and
radiative losses to the surrounding. The concentrators can be rotated so that the sun
rays always focus on absorber tube. This movement is called tracking. s the fluid
• 4hotovoltaic conversion is the direct conversion of sunlight into electricity at the atomic
level with no intervening heat engines.
• Some materials exhibit a property known as the photoelectric effect that causes them to
absorb photons of light and release electrons. (hen these free electrons are capturedan electric current result that can be used as electricity.
• The photoelectric effect was first noted by )ec-uerel in 1"7 when light was incident on
an electrode in an electrolyte solution. 3n 17%# researchers at B$ and )ell 9aboratoriesbuilt first photovoltaic module of p and n types of semiconductors.
'OR(ING OF &*O)O,OL)AIC CELL
• 4hotovoltaic cell or solar cells are made of semiconductor materials such as silicon.
• thin semiconductor wafer is specially treated to form an electric field positive on one
side and negative on the other.
• (hen light energy strikes the solar cells electrons are knocked loose from the atoms in
the semiconductor material. 3f electrical conductors are attached to the positive and
negative sides forming an electrical circuit the electrons can be captured in the form ofan electric current ie electricity.
• number of solar cells electrically connected to each other and mounted in a support
structure or frame is called a photovoltaic module. The current produced is directlydependent on how much light strikes the module.
• Multiple modules can be wired together to form an array. 3n general the larger the area
of a module or array the more electricity that will be produced.
• 4hotovoltaic modules and arrays produces direct2current 0@$: electricity.
• They can b connected in both series and parallel electrical arrangements to produce any
re-uired voltage and current combinations.
A&&LICA)IONS OF &*O)O,OL)AIC CELL
• $alculators
• (atches
• (ater 4umping
• Bemote )uildings
• $ommunications
• Satellites and Space Fehicles
SO!AR '(ST(!AT(ON
• There is an important need for clean pure drinking water in many developing countries.
+ften water sources contain dissolved salts and harmful bacteria and therefore cannotbe used for drinking. 3n addition there are many coastal locations where sea water isabundant but potable water is not available.
• @istillation is one of many processes that can be used for water purification. This
re-uires an energy input as heatG solar radiation can be the source of energy. 3n thisprocess water is evaporated thus separating water vapour from dissolved matter which
is condensed as pure water.
'OR(ING OF SOLAR IS)ILA)ION
• 3t consists of a blackened basin containing saline water at a shallow depth over which a
transparent air tight cover completely closes the space above the basin.
• The incident solar radiation is transmitted through the transparent cover and is absorbed
as heat by a black surface 0basin: in contact with the water to be distilled.
• The water is thus heated and gives off water vapour. The vapour condenses on the
transparent cover which is at a lower temperature because it is in contact with theambient air and runs down into a gutter from where it is fed to a storage tank.
•Efficiencies of !%8 are typical. @aily output as a function of solar irradiation is greatest inthe early evening when the feed water is still hot but when outside temperatures arefalling.
• Tide of the sea is used for running the water turbine. The ocean tides contain large
amount of potential energy which is used for power generation.
• Tidal power is predictable and relies on the gravitational pull of the moon and the sun to
create currents in the oceans.
• @ue to the contours of the earth?s surface there is une-ual heating of the earth from the
sun which generates wind.
• This wind blowing over water makes ocean waves.
• (ave power refers to the energy of ocean waves and the capture of that energy to do
useful work.
'OR(ING OF )IAL &O'ER &LAN)
• @uring the high tide period the water flows from sea into the tidal basin through the
water turbine as the level of tide is more than the water level in the tidal basin. Thisoperates the turbine and ultimately the generator.
• @uring the low tide period the water flows from tidal basin to sea as the water level in thebasin is more than that of the tide in the sea. @uring this period also the flowing waterturns turbine and generates the power.
• The generation of power stops only when sea level and tidal level are e-ual.
A,AN)AGES OF 'A,E ENERG-
• (aves are free and will not run out so the cost is in building the power station.
• (ave power does not produce green house gases.
ISA,AN)AGES OF 'A,E ENERG- • (aves can be big or small so you may not always be able to generate electricity.
• Hou need to find a way of transporting the electricity from the sea onto the land.
• &ot many people have tired to generate electricity this way yet so the e-uipment is
expensive.
A,AN)AGES OF )IAL ENERG-
• Tides are free once the power station has been built and will not run out.
• &o green house gases are produced when we make the electricity.
• The plant consists of two parts. The digester which is a well containing the animal waste
in the form of slurry and the dome which floats on the slurry and serves as the gasholder.
• The digester is below ground level. vertical partition wall divides it into two e-ual parts
and serves to direct the flow of the slurry.
• Two pipe lines leads to digester bottom2 one for feeding slurry and other to remove the
spent slurry called sludge which comes out after it has undergone fermentation.• The sludge contains nitrogen phosphorous and potassium which acts as excellent
fertilizers.
• The diameter of digester ranges from 1.! m to 5 m and depth from " to 5 m.
• The gas generation process occurs in two stages. 3n first stage the complex organic
substances contained in the waste are acted upon by a certain kind of bacteria calledacid former and are broken up into small chain simple acids. 3n second stage theseacids are acted upon by another kind of bacteria which completes fermentation.
• @ue to fermentation reaction the density of slurry decreases and it moves up and flow
into second chamber and then into the sludge. The gas liberated during the process is
collected in the dome.
A,AN)AGE OF .IOGAS &LAN)
• 3t converts natural organic waste into fertilizer which is free from harmful synthetic
chemicals.
• 3t is eco2friendly energy production. The calorific value of biogas is e-ual to that of half
litre of diesel oil. 3t is capable of replacing wood hard coal kerosene etc.
• 3t helps considerable workload reduction in rural areas.
• 3t significantly lowers the green house effects on the earth?s atmosphere.
ISA,AN)AGE OF .IOGAS &LAN) • ,ormation of sulphurous compounds can lead to odour.
• )io diesel is a renewable fuel derived from vegetable oils such as soybean oil corn oil
sunflower oil cotton seed oil rubber seed oil etc.
• 3t is refined into fuel which can be burned in diesel engines and buses.
• 3t can also be made by combining alcohol with vegetable oil or recycled cooking greases
or oils 0eg yellow grease:.
• 3t can be used as an additive to reduce vehicle emissions 0typically !68: or in its pure
form 0)3++: as a renewable alternative fuel for diesel engines.
A,AN)AGES OF .IO IESEL
• 3t is renewable and clean burning fuel.
• 3t has high lubricity and fuel efficiency.
• 3t emits very low green house gases.
• 3t is bio gradable non toxic non hazardous non flammable.
)uel Cells
• fuel cell is a device that generates electricity by a chemical reaction. Every fuel cell has
two electrodes one positive and one negative called anode and cathode respectively.The reaction that produces electricity takes place at the electrodes.
• Every fuel cell also has an electrolyte which carries electrically charged particles from
one electrode to the other and a catalyst which speeds the reaction at the electrodes.
• 'ydrogen is the basic fuel along with oxygen. ,uel cells generate electricity with very
little pollution as much of the hydrogen and oxygen used ultimately combines to formharmless by product ie water.
1. (hat are conventional 0non renewable: and non conventional 0renewable: sources ofenergyI *ive examples of each.@ec !667 0#:+B 9ist out renewable and non renewable sources of energy. May !61!@ec !66 0!:+B @ifferentiate between renewable and non renewable source of energy. @ec!61! 0#:
!. State the fuels used in following types of power plants Thermal and &uclear @ec!611 0!:
". @raw a sketch of thermal power plant and explain its workingI State two application of
it. May !6160#:
#. @raw labeled sketch with working of nuclear power plant. State applications of it. May !61! May !667
0#:%. Explain use of hydraulic energy to generate electricity.
May !611 0#:5. @escribe the working principle of tidal power plant with suitable sketch. @ec !611 May
!611 0#:<. State advantages and disadvantages of solar energy. @ec !611 May !611
May !616 0#:. @raw a sketch of solar water heater and describe its working in brief.
+B @raw a labeled sketch of solar water heater. State any two advantages of solarenergy.
May !667
0#:7. Explain the use of solar energy to generate electricity with neat sketch. May
!66 0#:+B Explain photovoltaic cell working with a diagram. (rite its two applications. @ec!667 0#:
16.State various types of wind mills. May !660!:
11.@escribe the working principle of wind mill. @ec !6110#:
1!.(hat do you mean by geothermal energy sourceI Explain how this can be used.@ec !667 0#:
1".State advantages and disadvantages of tidal energy. @ec !61!May !667@ec !66 0#:
1#.@raw a labeled sketch of )iogas plant. State its advantages. May!66 0#:@raw a labeled sketch of )io2gas plant. State two applications of the same. @ec!66 0#:
1%.*ive advantages of $oncentric $ollectors. May !6110!:
15. Explain the working of solar distillation plant. @ec!61! 0#:
1<.(hat is biogas and bio massI State its applications. May!61! 0#:
