eme ch 2_energy ppt
TRANSCRIPT
Elements of Mechanical Engineering
Chapter 2. Energy
Mitesh D. Gohil
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Outline
1.Introduction to Energy
2.Solid fuels
3.Liquid fuel
4.Gaseous Fuels
5.Nuclear Energy
6.Solar Energy
7.Wind energy
8.Hydel Power
9.Biomass and Biomass energy
10.Environment issues like Global warming and ozone depletion
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1.1 Introduction to Energy
Energy
Energy has been defined as its capacity to do work in various forms to produce
the dynamic effect in a body.
Energy need…
Transportation,
Industry (Production machines, Construction, Textile, Refinery etc.),
Domestic (Electricity)
Power
Power is defined as the rate of doing the work. Power is produced in various
power plant in the form of mechanical and electrical power
Source of energy
1. Conventional / Non-renewable Sources: Fossil fuels, nuclear fuels
2. Non-conventional / Renewable Sources: Solar, hydro power, wind,
geothermal, tidal, biomass, Ocean thermal, wave etc.
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Conventional fuels
These fuels may be naturally occurring or be prepared fuels (artificial fuel)
Classified base on its phase
1) Solid fuels
2) Liquid fuels
3) Gaseous fuels
The elements and compounds which are commonly found in fuels are
1) Carbon and Hydrogen compounds
2) Oxygen
3) Nitrogen
4) Sulphur
5) Ash, Impurities and other incombustible matter
1.1 Introduction to Energy…continue
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1.2 Solid fuels
1) Naturally occurring :- Peat, Lignite, Bituminous, Anthracite
2) Prepared (artificial) :- Charcoal, Coke, Pulverised Coal, Bagasse etc.
Coal occurs naturally is the result of decay of vegetable matter because of
the prolonged action of bacteria, fungi, pressure and heat
Peat is the lowest form of coal which occurs during the conversion of wood
of coal, its further conversion is followed by lignite, bituminous and
anthracite form of coal
Calorific value (C.V.) of fuel
The amount of heat energy released due to complete combustion of unit quantity
of fuel when the products are cooled back to S.T.P. (1 atm., 25 °C) is called the
calorific value of fuel.
Solid & Liquid fuel :- C.V. measures in KJ/kg.
Gaseous fuels :- C.V. measures in KJ/𝑚3
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Analysis of solid fuel is generally carried out in following way.
1) Proximate Analysis
It will show principle constituents of a coal like fixed carbon, moisture,
volatile matter and ash in percentage by mass.
2) Ultimate Analysis
It is accurate chemical analysis in percentage by mass of a coal to determine
its constituents – carbon, hydrogen, oxygen, nitrogen, Sulphur and ash
This types of analysis is useful for the thermodynamic analysis of the reactive
system and for combustion calculations
Broad ultimate analysis of various types to dry coal is given below
Analysis of solid fuel
Carbon 50 - 98 %
Oxygen 2 - 40 %
Ash 2 – 30 %
Sulphur 0.5 - 7 %
Hydrogen 2 – 5.5 %
Nitrogen 0.5 – 3 %
1.2 Solid fuels...continue
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1) Wood
Not consider as a commercial fuel
Still used as a fuel for cooking and heating
C.V. Varies with kind and moisture contain in it
2) Peat
It is a mixture of moisture (upto 90%) and decayed vegetable matter.
Used for gas producer plants
3) Coal
Conversion of peat from lignite to anthracite in earth crest due to
pressure and heat over a period of millions years.
During formation of peat losses moisture, Hydrogen, Nitrogen,
Sulphur and volatile matter progressively while its carbon content
and the heating value of the fuel increases
1.2 Solid fuels...continue
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4) Charcoal
Prepared (Artificial) by dry distillation of wood, when wood is burned in retorts
with insufficient air, the volatile matter is reduced and leaves behind the charcoal
as residue.
By Products: Methyl alcohol, Acetic acid, Acetone, Gaseous compounds and Tar.
No Sulphur content
Porous in nature
C.V. = 25 MJ/kg (approximately)
5) Coke
Obtained by destructive distillation of soft coal in close retorts in absence of air.
Coal decomposed thermally, this process is called Carbonization.
By Product : Coke oven gas
6) Briquetted coal
Small coal during mining are briquetted by heat, pressure and a binder
So that it can burned easily in standard equipment.
7) Anthracite
Highest Grade (C.V. = 33 to 35 MJ/kg), 92 % carbon contain (approx.)
Shiny black, hard brittle.
Used for Power Generation in boiler
1.2 Solid fuels...continue
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Coal mine in India
1. Gondwana coal fields
Bituminous and SubBituminous
Situated in the regions of Maharashtra, Bihar, Madhya
Pradesh, Orissa and Andhra Pradesh and Bengal
2. Tertial Coal Field
Lignite
Situated in region of Tamil Nadu (Neyueli), Rajasthan, Assam
and Kashmir)
1.2 Solid fuels...continue
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Include natural fuel like crude petroleum and the
Artificially prepared fuels like tar, alcohols
Classified based on use
Light Oils :- Used in I.C. engine
Heavy oils :- Used in Furnaces
Hydrocarbon compositions, chemical formula CnHm
Crude Petroleum
Forms due to anaerobic bacterial action under very high pressures and
temperature from the decay of buried animal and vegetable debris million
years ago.
Main compounds of crude petroleum
Paraffin (CnH2n+2, saturated chain)
Olefin (CnH2n, unsaturated chain)
Naphthenes (CnH2n, saturated ring)
Aromatics or Benzenes (CnH2n−6, unsaturated ring)
1.3 Liquid fuels
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1) Paraffin (𝐂𝐧𝐇𝟐𝐧+𝟐, 𝐬𝐚𝐭𝐮𝐫𝐚𝐭𝐞𝐝 𝐜𝐡𝐚𝐢𝐧)
Suffix “ane” , Example:- Methane (CH4), Ethane (C2H6), Propane (C3H8),Butane(C4H10), Pentane(C5H12)
Usually stable, low specific gravity.
n = 1 to 4 (gases) = 5 to 18 (liquid) ≥ 18 (solid)
Types : Paraffin & Iso paraffins
Iso paraffins have same number of carbon & hydrogen atoms but of different
molecular structure.
For Iso-paraffin, Physical and chemical properties may differ slightly but
combustion properties widely.
Example: Iso octane(Iso-paraffin) has smooth combustion characteristics in SI
engine while n-octane(paraffin) has high knocking tendency.
2) Olefin (𝐂𝐧𝐇𝟐𝐧, 𝐮𝐧𝐬𝐚𝐭𝐮𝐫𝐚𝐭𝐞𝐝 𝐜𝐡𝐚𝐢𝐧)
Unsaturated means insufficient hydrogen atom
Olefin contain one double bond with a carbon atom
Good combustion characteristics
Forms during oil cracking (Oil cracking is process to breakdown long chain
hydrocarbon and form light hydrocarbon, depends on temperature and
catalysts)
1.3 Liquid fuels…continue
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1.3 Liquid fuels…continue
3) Naphthenes (𝐂𝐧𝐇𝟐𝐧, saturated ring)
Stable
Combustion characteristics are similar to iso paraffins and physical
properties are similar to n-paraffins
4) Aromatics or Benzenes (𝐂𝐧𝐇𝟐𝐧−𝟔, unsaturated ring)
Thermodynamic properties are similar to naphthenes but desired
combustion characteristics for use in SI engine due to which those
compounds are added in gasoline to increase their octane rating.
However compounds have a tendency to smoke during burning
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1.3 Liquid fuels…continue
Advantages of Liquid fuels
High C.V.
Easy to store, handle and control during combustion
It keeps the power plant neat and clean in appearance
Elimination of wear and tear of grate bars in steam power plant
Change in load in a power plant can easily be met
Combustion losses are low
Disadvantage of Liquid fuels: Costly
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1.4 Gaseous Fuels
Include natural gas and the artificially prepared fuels like acetylene (C2H2),
methane (CH4), ethylene (C2H4) or the industrial gases like coke over gas,
blast furnace gas, producer gas etc.
Advantages of Gaseous fuel
Produced and distribute easily
Low grade fuels (coal) can be used for gasification.
Easy to store, handle and control during combustion
It keeps the power plant neat and clean in appearance
Elimination of wear and tear of grate bars in steam power plant
Change in load in a power plant can easily be met
Combustion losses are low
Smoke and ash are eliminated14
1.4 Gaseous Fuels…continue
1. Natural gas
Found in the upper part of oil or gas wells
Odourless and colour less
Mainly contain methane, small quantity of ethane, propane and high H-C
Also contains CO2, N2, H2S
CV = 37 to 46 MJ/m3
Application:- Gas engine & heating
2. Coke oven gas
It produced as by product during carbonization of coal to make coke in closed
retorts at temperature 600° C to 1000° C
Application :- Industrial heating and power generation
3. Blue water gas
Produced by blowing steam through
incandescent bed of fuel containing
carbon
Contains :- Mixture of CO, CO2, H2
It burns with blue flame
CV = 9 to 11 MJ//m3
Application:- Domestic Lighting
4. Producer gas
Partial (incomplete) gasification
of solid fuels
Mainly contains :- N2
Other gases:- CO, CO2, H2
Low C.V.
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1.4 Gaseous Fuels…continue
Alternative fuel
1. Bagasse
The Dry pulpy residue left over after the extraction of juice form sugar cane in
sugar industry is called bagasse
By mass it contain
C = 45%
O2 = 46 %
H2 = 6 %
Ash = 3 %
Used in furnaces of boiler
2. Biogas
Produced by anaerobic digestion of organic matter
Raw material :- Cow dung, municipal waste, kitchen waste, animal excreta etc.
Bio gas contains mainly CH4 & CO2
Application:- Stoves, Power production in engine
CV is low but it is anti-knocking
Poor ignition quality16
1.4 Gaseous Fuels…continue
3. LPG (Liquidified Petroleum Gas)
Contain Propane and Butane which liquefies at 8.8 bar and 2.1 bar respectively at
normal atmospheric pressure.
High CV
Stored in steel cylinder for domestic and industrial use.
Also used in automobiles because it is high anti-knocking and produce less pollutants
4. CNG (Compressed Natural Gas)
Used to run automobiles with CNG Conversion kits for SI engine
Emission level is very less compare to petrol
5. Hydrogen Gas
Produced by electrolysis method and is very expensive.
Also available as by product from chemical industries like caustic soda.
It provides large amount of energy compare to petrol and diesel.
But, Problem in using as it is high explosive in nature
Hydrogen is used as fuel for power generation in fuel cells. 17
1.5 Nuclear Energy
Used for power generation in nuclear power plant (Atomic power plant)
Uranium (U235), thorium and Plutonium (Pu239) are used as fuel.
Heat produce due to atomic fission process in which heavy nucleus (Uranium)
is split into two or more lighter nucleus having combine mass less than parent
nucleus.
Fission is carried out by bombarding slow moving neutrons on the atom of
fuel used in a nuclear reactor.
Reduced mass is converted into enormous energy based on Einstein mass
energy equation
E = ∆m c2
Where, ∆m = mass defect in kg
C = velocity of light =3 × 108 m/s
Complete fission of U235 produce 82000 MJ/g energy. 18
1.5 Nuclear Energy…continue
Advantages of nuclear energy
Reduced demand of fossil fuels
Transportation and storage is easy
Produces large power
Non Pollution
Disadvantages of nuclear energy
Problem of radioactive waste disposal
High safety needed
Technology cost is high
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Sun produced energy through continuous nuclear fusion.
Two deuterium (heavy Hydrogen) combines to form on atom of helium and
during the process releases large quantum of energy.
Sun send out the maximum radiation power 1357 W/m2 on earth.
Solar Energy is utilized with help of Solar collector (heat energy) and Photo-
Voltaic cell (electrical energy)
Solar collector is a device for absorbing the solar radiation on a surface called
absorber and transfer that heat energy to fluid like water or air.
Photo-Voltaic cell contain P-N junction which produces e.m.f. when solar
radiation falls on the surface of that cell.
Different type of flat plate and concentrating collectors are shown in Fig.
1.6 Solar Energy
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1.6 Solar Energy…continue
Fig. Flat plate collector
Flat Plate Collector
Tubes are generally made of copper material due to its high thermal
conductivity.
Water or thermic fluid (oil) and air could be used as heat transfer medium.
It can produced maximum temperature up to 120°21
1.6 Solar Energy…continue
Fig. Concentrating solar collectors (a) Linear Fresnel collector, (b) dish
collector (c) Parabolic trough collector (d) Central tower receiver
Concentrating collectors can produce high temperature up to 1800° C.
So, these collectors are more suitable for power generation.22
1.6 Solar Energy…continue
Advantages of solar energy
Inexhaustible and abundance
Pollution free
Low operating cost and maintenance cost
No fuel storage and transportation cost
Directly converted into electrical energy via Photo-Voltaic cells
Many options are available to utilize the energy (Flat plate
collector, Concentrating collector, Photo-Voltaic cells etc.)
Limitations of solar energy
Energy is dilute and spread out
Average power obtain is only 1000 W/m2 (in hottest region), So
large collector area required.
Energy intensity of radiation depends on weather and day hour.
Energy is not available at night and seasonal variation in the
intensity23
Indirect evidence of solar energy
Unequal heating of the atmosphere by the sun produces the air flow called
planetary winds
Also local winds are produced due to different heating of land and water in
coastal areas.
High wind speed is available in sea coast and hilly terrains.
High wind speed (3 to 10 m/s) desirable to drive the wind turbine.
Wind drives the wind turbine and power produced in electric generator.
Application
Electric power generation, batteries charging, water pumping for irrigation
1.7 Wind energy
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Advantages of wind energy
Free available and inexhaustible
Clean, non-polluting
Low maintenance and power cost
Disadvantage of wind energy
Capital cost high
Dilute and fluctuating in nature both magnitude and direction
Large variation during cyclone, hurricanes, and tornadoes may damage
the installation.
Design of system is difficult due to large variation of wind speed from
time to time and season.
Require energy storage system to ensure continuous power supply.
Actual efficiency is low (40 % Approx.)
Sound pollution
1.7 Wind energy…continue
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1.7 Wind energy…continue
Horizontal axis type wing turbine is
shown in fig.
Rotor has 2-3 propeller type blades, 2-
25 m in diameter.
Rotor blades are assembled on a hub.
Electromagnetic brakes are provided to
stop the rotor if wind speed exceed the
design speed.
Gear box is provided to increase speed
of shaft the ratio 1:100Fig. Horizontal axis type wind turbine
The hub, brakes, gear box, generator with electric control are housed in a box
called nacelle.
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Hydro-electric power plant or Hydel plant utilize the potential energy of
water to move hydraulic turbine which coupled to electric generators.
Large amount of water is collected during rainy season in a reservoir behind
dam.
Hydel power generally used as peak load plant to fulfilled maximum demand
during peak hours.
So, hydel power plant is interconnected with steam power plant (or base load
plant)
1.8 Hydel Power
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1.8 Hydel Power…continue
Fig. Hydro power plant with impulse turbine (Pelton turbine)
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1.8 Hydel Power…continue
Fig. Hydro power plant with Reaction turbine (Francis turbine)
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1.8 Hydel Power…continue
Main components
1) Reservoir: To store water during rainy season and supplies the same in dry season.
2) Dam: It is structure of considerable height built across the river. Function is provide
working head of water and increase the storage capacity of reservoir
3) Penstock: It is provide to carry water from dam to hydraulic turbines.
4) Hydraulic Turbine : It uses the pressure and kinetic energy of water that coming out
from penstock and produce mechanical work in the shaft.
5) Trash rack: It is made of steel bars to prevent the entry of debris from dam into
penstock.
6) Gate: The gate is provided for controlling of flow of water from reservoir to hydraulic
turbine through penstock
7) Surge tank: It prevent the penstock from busting due to sudden increase in pressure
called water hammer, caused by sudden closing of gates to turbine.
8) Power house: It consist of hydraulic and electrical equipment where water energy is
converted into electrical energy 30
1.8 Hydel Power…continue
Operation
In the penstock P.E. of water converted into K.E. that strikes on turbine in
the form of jet.
So the turbine rotates and a generator coupled to hydraulic turbine converts
the available mechanical energy into electrical energy.
The speed of turbine depends on the head, specific speed and the power.
The electrical power generated is controlled by the governing mechanism
attached to hydraulic turbine which controls the quantity of water to be
supplied to the turbine according to the load on the system.
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Advantages of hydel energy
Low cost of power generation,
No fuel need
Reliable without uncertainty
Non-polluting
Life is about 50 years.
Disadvantages of hydel energy
Availability of power depends on rainfall
Required long transmission lines.
High capital cost
Disturbs ecology of area.
Time require for establishment of plant.
1.8 Hydel Power…continue
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Biomass is on organic matter produced by plants both grown on load (terrestrial
biomass) and grown on water (aquatic biomass) and their derivatives and animal
manure.
The energy obtain form biomass is called biomass energy.
Biomass is obtained from cultivated fields, living organism both on land and
water, municipal waste, animal excreta, forest wastes, agricultural waste etc.
Biogas is produced by aerobic or anaerobic decomposition of organic waste by
suitable bacteria.
Application of Biogas: Cooking, fuel in engine, pumping of water, electric
generation etc.
Biofuels: Biofuels can be broadly defined as solid, liquid or gaseous fuel from
recently dead biological material from commonly used plants.
Most commonly used biofuels are as liquid fuels for automotive use.
Vegetable oils like karanji oil (pongamia pinnata tree), sun flower oil, jatropha
oil can used with diesel upto 30 % to run diesel engines.
These oils are heated so as to reduce their viscosity before supplied to the
cylinder directly or blended with diesel called biodiesel.
1.9 Biomass and Biomass energy
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1.10 Environment issues like Global warming and ozone depletion
Ozone Depletion
Ozone layer (O3) in stratosphere (10-50 km form earth) absorbed Ultraviolet
rays emitted by sun and protects us against harmful effects like skin cancer.
O3 + Cl → ClO + O2 CFC’s (Chloroflouro carbons) refrigerants emitted from earth reacts with ozone
layer and deplete the ozone layer, this called ozone hole.
Greenhouse effect and Global warming
Certain gases (CO2, CH4) emitted by industries reach to stratosphere and form
layer which acts a glass in a green house. These gases are called greenhouse
gases (GHGs).
GHGs produced due to industrial process, thermal power plant, reducing forest.
In greenhouse effect, the solar heat of short wave length enters the glass house
but does not get radiated back through glass and converts in heat having long
wave radiations. These radiations are reflected by the glass and heat is trapped
inside the glass house to keep the plant green.
Similarly solar heat enters the layer formed by the gases emitted from earth’s
surface but does not get radiated back to space due to different wave length. It
tends to increase the temperature on the earth surface.
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Other effects of pollutants and thermal pollution
1) Acid rains
Acid precipitation is the return to earth of the oxides of Sulphur and Nitrogen in
acid form. It may be form of acid rain or acid snow.
SO2 + H2O → H2SO4NOX + H2O → HNO3
Effect: Decrease the PH value of river, lakes and well, so it affects the aquatic
life, reduce fertility of soil, damage national monuments and building.
2) Thermal Pollution
Cooling water of steam power plant carry enormous amount of heat which
discharge into rivers, lake, sea or reservoir through power plant. It is called
thermal pollution.
Water with impurity and chlorine residues harmful for aquatic life.
Pumping can suck fishes or other live species which lead to injury or death.
Controlling method: Construct separate cooling tower that also increase the
efficiency of plant.
1.10 Environment issues like Global warming and ozone depletion
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Que. Which are common solid fuels ? Write in brief about each of them.
Define calorific value of fuel.
GTU : Jan 2011
Que. What are different types of coal ? State their properties. GTU : April 2010
Que. Differentiate between the following : Lignite and bituminous coal GTU : Dec 2010
Que. List the various liquid fuels. GTU : Dec 2008
Que. List the various liquid fuels. State its merits over solid fuels. GTU : May 2012
Que. State advantages of liquid fuels over solid fuels. GTU : Dec 2008
Que. State the advantages of gaseous fuels over solid and liquid fuels. GTU : Jan 2010
Que. Write advantages of gaseous fuels over other fuels. GTU : June 2011
Que. Write short note on LPG GTU : June 2011
Que. Write short note on CNG GTU : June 2009
Que. Explain prospects of following alternative fuels : Compressed natural gas GTU : Dec 2010
Que. Explain Prospects of following alternative fuels : Hydrogen gas GTU : Dec 2010
Questions of GTU Exam
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Thank You…
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