Eme ch 2_energy ppt

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


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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


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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)


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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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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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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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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


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


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


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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Fig. Hydro power plant with Reaction turbine (Francis turbine)

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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


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.


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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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