1. study of sources of energy

ME-161
Introduction to Mechanical
Engineering
LEVEL-1, TERM-I
Adib Bin Rashid
Capt
Instructor Class C
Mechanical Engineering Department

Study of sources of energy: conventional and renewable
Adib Bin Rashid
Capt
Instructor Class C
Mechanical Engineering Department

Energy engineering
• Energy engineering or Energy systems is a broad field of engineering dealing
with energy efficiency, energy services, facility management, plant
engineering, environmental compliance and alternative energy technologies.

Mechanical Energy:
•Defined as energy which can be used to raise a weight.
•Can be easily and efficiently converted into other energy forms.
Electrical Energy:
•Defined as that class of energy associated with the flow or
accumulation of electrons.
•Large quantities of electrical energy are transferred over long
distances with the use of high-voltage transmission lines.
•Can be converted into other energy forms.

Energy: Different forms
Electromagnetic Energy:
•Defined as that form of energy associated with
electromagnetic radiation.
•Extensively employed in nuclear energy study.
Chemical Energy:
•Defined as energy that is released as the result of
electron interactions in which
two or more atoms and/or molecules combine to
produce a more stable chemical compound.
•Commonly reported in the units of energy per unit
mass or “mole” of fuel reactant

Sources of energy :-
There are two main sources of energy. They are
conventional and non conventional sources of energy.
i) Conventional sources of energy :- are wood, flowing
water and fossil fuels (coal, petroleum, natural gas).
ii) Non conventional sources of energy :- are solar energy,
wind energy, biomass energy, ocean energy (tidal
energy, wave energy, ocean thermal energy),
geothermal energy, nuclear energy etc.
Some sources of energy are renewable like sun, wind,
flowing water, ocean, wood, biomass etc.
Some sources of energy are non renewable like coal,
petroleum and natural gas.

Conventional sources of energy :-
Fossil fuels :-
are fuels formed inside the earth from the remains of plants and animals
after millions of years. The fossil fuels are coal, petroleum and natural
gas. Fossil fuels are non renewable sources of energy so they should be
conserved and used judiciously.
Disadvantages of fossil fuels :-
i) Burning of fossil fuels release gases and harmful particles which causes air
pollution.
ii) Burning of fossil fuels release acidic oxides of sulphur and nitrogen which
causes acid rain which is harmful for living organisms, affects soil and
water, causes damage to buildings, corrosion of metals etc.
iii) Burning of fossil fuels release a large amount of carbon dioxide gas which
increases the temperature of the atmosphere and causes global warming
(green house effect).

Fossil Fuels:
Fossil Fuels are formed from Living things millions of years ago. They are
Hydrocarbons and are Finite Fuels ie. They will run out in the future
and cannot be regenerated. There are three main Fossil Fuels:
Coal, Oil and Gas
Oil: This was formed
by dead sea
creatures falling to
the sea-bed where
they were subjected
to chemical change
by Bacteria.
Coal: This was
formed by the decay
of Vegetation which
was subjected to
heat and pressure
over a very long
period of time.
Gas was formed in
much the same
way as Oil. It is
often collected
when drilling for
Oil.

Classification of Fuel
Fuels may be classified into the following general
terms:
1. Solid Fuel
2. Liquid Fuels
3. Gaseous Fuel
Each of these fuels may be subdivided into the
following categories-
1. Natural Fuels
2. Prepared Fuels

Solid Fuel
• Wood: At one time it was an extensively used
fuel. It consists of mainly carbon and hydrogen.
• Peat: It is a spongy humid substance and
contains about 30% water. It has to be dried
before use. It is the first stage in the formation of
coal.
• Lignite or brown coal: It is the next stage of peat
in the coal formation and an intermediate variety
between bituminous coal and peat. It contains
nearly 40% moisture and 60% of carbon.

Solid Fuel
• Bituminous Coal: It represents the next stage
of lignite in the coal formation and contains
very little moisture(4-6%) and 75 to 90% of
carbon.
• Anthracite Coal: It represents the final stage
of coal formation and contains 90% or more
carbon.

Solid Fuel
• Wood Charcoal: It is made by heating wood
with a limited supply of air to a temperature
not less than 280˚C.
• Briquetted Coal: It is produced from finely
ground coal by moulding under pressure with
or without a binding material.
• Pulverised Coal: The low grade coal with high
ash content is powdered to produce
pulverised coal.

Coal composition and rank:
• All of the fossil fuels are produced from the fossilization
of carbohydrate compounds.
• Coal, the most abundant fossil fuel, is thought to be
fossilized vegetation.
• It is estimated that at least 20 ft of compacted
vegetation was necessary to produce a 1-ft-thick seam
of coal.
• This compacted coal is then converted into peat, a low-
grade fuel, then into brown, then into lignite, then into
sub bituminous coal, then into bituminous coal, and
finally into anthracitic coal.
• Aging process progresses, coal becomes harder,
hydrogen and oxygen fractions decrease, moisture
content decreases, and carbon fraction increases.

• Coal is an organic rock (as opposed to most
other rocks in the earth's crust, such as clays
and sandstone, which are inorganic).
• It contains mostly carbon (C), but it also has
hydrogen (H), oxygen (O), sulfur (S) and
nitrogen (N), as well as some inorganic
constituents (minerals) and water (H2O).

It is estimated that at least 20 ft of compacted
vegetation was necessary to produce a 1-ft-thick
seam of coal .

There are several different systems used for classifying coal, but the American
Society for Testing Materials (ASTM) has developed a method for ranking coal into
four major classifications:
Class I Coals: Anthracitic coals
 Class II Coals: Bituminous coals
 Class III Coals: Sub bituminous coals
Class IV Coals: Lignite coals

Liquid Fuels
• Almost all the commercial liquid fuels are derived from
natural petroleum. The liquid fuels consist of
hydrocarbons.
• The natural petroleum may be separated into petrol or
gasoline, paraffin oil or kerosene, fuel oils and
lubricating oil by boiling the crude oil at different
temperature and subsequent fractional distillation.
• The following liquid fuels are important from the
subjects point of view.

Liquid Fuels
1. Petrol or gasoline: It is the lightest and most volatile liquid fuel, mainly
used for light petrol engines. It is distilled at a temperature from 65˚-
220˚C.
2. Kerosene or Paraffin oil: It is the heavier and less
volatile fuel than the petrol, and is used as heating
and lighting fuel. It is distilled from 220˚-345˚C
3. Heavy Fuel oil: The liquid fuels distilled after petrol
and kerosene are known as heavy fuel oil. These oils
are used in diesel engines and oil fired boilers. They
are distilled at a temperature from 345˚-470˚C.

Merits and Demerits of Liquid Fuel over
Solid Fuel
Following are the merits and demerits Solid Fuel:
Merits:
1. Higher Calorific value.
2. Lower storage capacity required.
3. Better economy in handling.
4. Better control of consumption by using valves.
5. Practically no ashes.
6. Non-deterioration in storage.
7. Non-corrosion of boiler plants.
8. Higher efficiency.

Merits and Demerits of Liquid Fuel
over Solid Fuel
Demerits:
1. Higher cost
2. Greater risk of fire.
3. Costly containers are required for storage
and transport.

Gaseous Fuel
The natural gas is, usually found in or near the petroleum
fields, under the earth’s surface. It essentially consists of
marsh gas or methane(CH4) together with small amounts
of other gases such as ethane(C2H6), carbon dioxide(CO2).
The following gaseous fuels are important from subject
point of view.
1. Coal gas: It is obtained by carbonization of coal and
consists mainly of H2,CO and various hydrocarbons.
2. Producer Gas: It is obtained by the partial combustion
of coal, coke, anthracite coal or charcoal in a mixed air-
steam blast.

Gaseous Fuel
• Water gas: It is a mixture of H2 and CO and is
made by passing steam over incandescent coke.
• Mond Gas: It is produced by passing air and a
large amount of steam over waste coal at about
650C.
• Blast Furnace Gas: It is a by-product in the
production of pig iron in the blast furnace.
• Coke oven gas: It is by-product from coke oven
and is obtained by the carbonization of
bituminous coal.

Merits and Demerits of Gaseous Fuel:
Merits:
1. The supply of fuel gas and hence the temperature of
furnace is easily and accurately controlled.
2. The high temperature is obtained at a moderate cost
by pre-heating gas and air with heat of waste gases of
combustion.
3. They are directly used in internal combustion engine.
4. They do not produce ash or smoke.
5. They undergo complete combustion with minimum
air supply.

Merits and Demerits of Gaseous Fuel
Demerits:
1. They are readily inflammable.
2. They require large storage capacity.

Requirements of Good Fuel
1. A good fuel should have low ignition point.
2. It should have a high calorific value.
3. It should freely burn with a high efficiency, one
it is ignited.
4. It should not produce harmful gases.
5. It should produce least quality of smoke and
gases.
6. It should be economical, easy to store and
convenient for transportation.

Coal Analysis
• Proximate Analysis:
It gives the mass fractions of fixed carbon (FC), volatile matter (VM), ash (A), and moisture (M) in the
coal.
Can be determined by weighing, heating and burning a small sample of powdered coal.
Procedures:
 Coal sample is carefully weighed and then heated to 110ºC for 20 min. Sample is weighed again and
mass loss is divided by the original mass to obtain the moisture fraction (M).
 Remaining sample is heated to 954ºC in a closed container for 7 min. Sample is then reweighed and
resulting mass loss is divided by the original mass to obtain the fraction of volatile matter (VM).
 Sample is then heated to 732ºC in an open crucible until it is completely burned. Residue is then
weighed and final weight is divided by original weight to obtain ash fraction (A).
 Mass fraction of fixed carbon (FC) is obtained by subtracting the M, VM and A from unity.

Coal Analysis
Ultimate Analysis:
o The chemical approach to characterizing coals is to determine the
amounts of the principal chemical elements in them.
o In the jargon of the coal business, this procedure is called the
ultimate analysis of coal.
o It is a laboratory analysis that lists the mass fractions of carbon
(C), hydrogen (H2), oxygen (O2), nitrogen (N2), and sulfur (S) in
the coal along with higher heating value.

Calorific Value of Fuel:
It is defined as the amount of heat produced when
unit quantity of fuel is completely burnt under
standard conditions.
It is expressed as kcal per kg or kcal, per cubic
meter of gaseous fuel.
Two ways:
(i) Higher calorific value (HCV) and
(ii) Lower calorific value (LCV).

(i) The higher or gross of calorific value is the total
amount of heat produced when unit quantity of
fuel is burnt completely and the products of
combustion have been cooled to room
temperature.
(ii) The lower calorific value is the net amount of heat
produced when unit quantity of fuel is completely
burnt and the products of combustion are not
cooled to room temperature but are allowed to
escape.

The higher or gross of calorific value
According to Dulong’s Formula,
HCV=33800C+144000H2+9270S kJ/kg
or,
HCV=33800C+144000(H2 -O2/8) +9270S kJ/kg
The lower calorific value
L.C.V= H.C.V- (ms X 2466 kJ/kg)

Problem - 1.
The percentage composition by weight of a sample
of coal is given as: C = 65.50%, H2 = 6.65%, O2 =
17.50%, S =1.80%. Using Dulong’s formula,
calculate the calorific (heating) value of coal .
Problem - 2.
A sample of coal has the composition by weight: C
= 70%, H2 = 8%, O2 = 7%, N2 = 3%, S =2% and ash
10%. Using Dulong’s formula, calculate the
calorific (heating) value of coal.

Thermal power plants :-
• In thermal power plants the heat energy
produced by burning fossil fuels like coal,
petroleum or natural gas is used to heat water
and change it into steam which rotates the
turbines of generators to produce electricity.

Hydro power plants :-
• In hydro power plants water from rivers are
stored by constructing dams. The water from
the dam flows down through pipes and rotates
the turbines of generators to produce
electricity.

Hydro power plants :-
• Advantages :-
i) Flowing water is a renewable source of energy.
ii) The electricity produced does not cause pollution.
iii) The water stored in dams can also be used to control floods and
for irrigation.
• Disadvantages :-
i) The initial cost is high.
ii) Large areas of land gets submerged and the decomposition of
vegetation produces methane gas which is a green house gas.
iii) It causes displacement of people from large areas of land.

Non conventional sources of Energy :-

Non conventional sources of Energy :-
Biomass energy :-
• The waste materials and dead parts of living
things are called biomass. Eg :- wood, animal
dung, vegetable waste, agricultural waste,
sewage etc. Biomass is decomposed by
anaerobic microorganisms to produce biogas.
• Biogas is a mixture of gases containing
methane, carbon dioxide, hydrogen and
hydrogen sulphide.

Biogas plant :-
The biogas plant has a large underground tank made of
bricks and cement. The lower part is the digester and the
upper part has a dome with a gas outlet. On one side of
the tank above the ground is a mixing tank and on the
other side is an overflow tank. Animal dung is mixed
with water in the mixing tank and the slurry is sent into
the digester. In the digester the slurry is decomposed by
anaerobic microorganisms and after a few days biogas is
produced. The gas is taken out through the gas outlet
and used for heating and lighting purposes. The slurry
left behind is rich in nitrogen and phosphorus and is
used as manure for crops.

Wind energy :-
Wind energy is used in wind mills which converts the kinetic energy of
the wind into mechanical or electrical energy. The kinetic energy of
wind can be used to do mechanical work like lifting water from
wells or grinding grains in flour mills. It can also be used to rotate
the turbines of generators to produce electricity.
A single wind mill produces only a small amount of electricity. So a
large number of wind mills in a large area are coupled together to
produce more electricity in wind energy farms.
Advantages :-
i) It is a renewable source of energy.
ii) It does not cause pollution.
iii) The recurring cost is less.
Disadvantages :-
i) Wind is not available at all times.
ii) It requires a large area of land.
iii) A minimum wind speed of 15 km/h is required

Solar energy :-
Solar energy is the energy obtained from the sun in the form of heat and light. The heat energy is
used in solar heating devices like solar cooker, solar water heater, solar furnaces etc. The light
energy is used in solar cells.
i) Solar cooker :- The box type solar cooker has an insulated box painted black inside. It is covered
by a glass plate which allows heat to enter inside but does not allow heat to escape out. It has
a mirror to reflect more sunlight into the box. The food to be cooked is kept in containers
inside the box It can produce a temperature of 100° to 140°.

Solar energy :-
ii) Solar water heater :- A solar water heater has an insulated box painted black inside with a
system of copper tubes. It is covered with a glass plate which allows heat to enter inside but
does not allow heat to escape out. When water flows through the copper tube it absorbs heat
and becomes hot

Solar cells :-
Solar cell is a device which converts solar energy into electrical energy. Solar cells are
made from semi conductors like silicon, germanium, gallium etc. A single solar cell
produces a voltage of about 0.5 to 1 V and produces about 0.7 W electricity. So
several solar cells are arranged in a solar panel to produce more electricity.

Solar cells :-
Advantages :-
i) It uses renewable source of energy.
ii) It produces electricity which does not cause pollution.
iii) It can be used in remote areas where there is no power supply.
Disadvantages :-
i) It uses a special grade of silicon which is expensive.
ii) Since silver is used for connecting the cells together it is more expensive.
iii) The current produced is DC and to convert it to AC increases the cost.

Energy from the sea :-
Energy from the sea is obtained in three different forms. They are Tidal energy, Sea wave
energy and Ocean thermal energy.
i) Tidal energy :-
The periodic rise and fall of sea level due to gravitational attraction of the moon causes
tides. A dam is constructed at a narrow opening between the land and sea. The
movement of water during high tide and low tide can be used to rotate the turbines
of generators to produce electricity.

ii) Sea wave energy :-
When strong wind blows over the sea it produces huge waves. The kinetic
energy of the moving waves can be used to rotate the turbines of generators
to produce electricity.

iii) Ocean thermal energy :-
There is a temperature difference between the warm surface water and the cold water at
the bottom of the oceans. This difference is about 20°C. The warm surface water is used
to boil liquid ammonia and the vapour is used to rotate the turbines of generators to
produce electricity. The cold water from the bottom is then pumped up to cool the
vapour back to liquid .

Geothermal energy :-
• The deeper regions of the earth’s crust is very hot. This heat melts rocks and
forms magma. The magma moves up and collects below at some places called
Hot spots. The underground water in contact with hot spot gets heated into
steam at high pressure. By drilling holes into hot spots the steam coming out can
be used to rotate turbines of generators to produce electricity.

Nuclear energy :-
Nuclear energy is the energy is the energy released during
nuclear reactions. During nuclear reactions some mass is
converted into energy and so a very large amount of energy is
produced during nuclear reactions. Nuclear reactions are of
two types. They are Nuclear fission and nuclear fusion

Nuclear energy :-
i) Nuclear fission :- is a nuclear reaction in which
the nucleus of a heavy atom like uranium,
plutonium, etc. splits into smaller nuclei with
the release of a large amount of energy. It is
used to make atom bombs and to produce
electricity. In a nuclear power plant the heat
energy produced by a controlled nuclear fission
chain reaction is used to produce steam which
rotates the turbines of generators to produce
electricity.

Nuclear energy :-
ii) Nuclear fusion :- is a nuclear reaction in which
small nuclei fuse together to form a heavier
nucleus with the release of a very large
amount of energy. The energy of sun is
produced by the fusion of hydrogen nuclei to
form helium nucleus. It is also used to make
the hydrogen bomb.

Nuclear energy :-
Advantages of nuclear energy :-
i) It produces a very large amount of energy per
unit mass than any other source of energy.
ii) If safety measures are taken, it is more
environment friendly than fossil fuels.
Disadvantages of nuclear energy :-
i) The cost of a nuclear reactor is very high.
ii) The availability of nuclear fuel is limited.
iii) Nuclear reactors produce harmful nuclear
wastes which is difficult to dispose.

1. study of sources of energy

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