Sources of energy

Energy
 Energy can neither be created nor destroyed.
 Energy comes in different forms and one form
can be converted to another.
 Many of the sources of energy ultimately derive from the
sun.
For example,
 If drop a plate from a height, the potential energy of the
is converted mostly to sound energy when it hits the ground.
 If we light a candle, the process is highly exothermic so that
the chemical energy in wax is converted heat energy and
light energy on burning.

What is a good source of
energy?
A good source of energy would be the one
 which would do a large amount of work per
unit volume or mass,
 be easily accessible,
 be easy to store and transport, and
 be economical.

Solar energy Wind energy Hydro power
Geothermal energy Bio-Mass Nuclear energy

We can divide all sources of
energy into two categories:
Non-Conventional sources of
energy
Conventional sources of energy

Non-Conventional sources of energy:
Those sources of energy which are being
produced continuously in nature and are
inexhaustible are called renewable or
non conventional sources of energy.
For example : Geothermal power
(power generated from the heat of the earth ) ;
solar energy; wind energy; tidal energy.

Conventional sources of energy:
Those sources of energy which have been
accumulated in nature over a very long period
of time (millions of years) and cannot be
quickly replaced if once exhausted are called
non-renewable sources of energy.
For example : Coal; natural gas; petroleum; electricity
(both hydel and thermal).

Thermal power plant
• Large amount of fossil fuels are burnt
every day in power stations to heat up
water and produce steam which further
runs the turbine to generate electricity.
• The term thermal power plant is used
since fuel is burnt to produce heat energy
which is converted into electrical energy.

Disadvantages of thermal
electricity.
• It causes air pollution.
• Carbon dioxide produced by burning these fuels
produces green house effect.
• The oxides of carbon, nitrogen and sulphur which
are released on burning these fuels lead to acid
rain which effects our water and soil resources.
• The fossil fuels are limited in nature and will be
exhausted soon if we continue to use them at
present rate.

Hydro electricity
Water flowing from higher level to
lower level has kinetic energy which can
be converted into mechanical energy
and then to electrical energy. Hydro
energy is easily storable, conventional,
renewable energy.

How is hydroelectricity
generated?
The water flowing in rivers or in water falls is collected in
dams. The water stored in the dam is then allowed to fall
from the top of the dam. Water turbine is located at the
bottom of the very deep inside the ground. The shaft of
this water turbine is connected to a generator. When the
water falls on the turbine at a high pressure, kinetic energy
of flowing water rotates water turbine which in turn
rotates the armature or the coil of the generator thereby
producing electricity.

Advantages of
hydroelectricity
• Hydro energy is renewed naturally by rain
water and melting of snow on high
mountains during summer.
• This energy can be stored in high level
reservoirs and can be used whenever
required which is not the case with wind
energy and solar energy.

Limitations of
hydroelectricity
• Hydro energy power project is a huge
project.
• High rise dams are constructed on rivers
which may give rise to a number of
environmental problems.

Solar energy
• Solar energy reaching the periphery of the
earth’s atmosphere is considered to be
constant and is called solar constant.
• Nearly half of it is absorbed while passing
through the atmosphere and the rest reaches
the earth’s surface.
• Solar energy in the form of heat is collected
through devices such as solar cookers, solar
cells and solar heaters.

Advantages of solar energy
• The principal advantages associated with solar cells
are that they have no moving parts.
• They can be set up in remote and inaccessible
hamlets in which laying of a power transmission line
may be expensive and not commercially viable.

Limitations of solar energy
• The solar energy received by earth is in scattered or diffused
form.
• Silicon which is used for making solar cells, is abundant in
nature but availability of the special grade silicon for making
solar cells is limited. The entire process of manufacture is still
very expensive, silver used for inter connection of the cells in
the panel further adds to the cost.
• Proper devices to concentrate and store solar energy are not
available as yet.

Biomass
Cow dung, various plant materials like the residue
after harvesting the crops, vegetable waste and
sewage are decomposed in absence of oxygen to
give biogas since the starting material is mainly cow
dung it is popularly known as gobar gas.

How is biomass generated?
The plant has a dome like structure built with bricks.
A slurry of cow dung and water is made in the mixing tank
from where it is fed into the digester. The digester is a sealed
chamber in which there is no oxygen. Anaerobic micro
organisms that do not require oxygen decompose or break
down complex compounds of the cow dung slurry. It takes a
few days for the decomposition process to be complete and
generate gasses like methane, carbon dioxide, hydrogen and
hydrogen sulphide. The bio gas is stored in the gas tank above
the digester from which they are drawn through pipes for use.

Biomass is an ideal fuel, as
 It has high calorific value.
 It does not produce smoke.
 It is very cheap and can be made very easily.
 It prevents water pollution.
 It does not create air pollution.

Wind energy
Wind is caused by unequal heating of different regions of the
earth by the sun. Energy possessed by moving wind is called
wind energy in fact wind has a wide application in our day to
day life.

Some important uses
of wind energy
• Airplanes make use of wind energy to
control their movement.
• Wind energy is used in sail boats.
• Wind energy is being used for generating
electricity.

How does a windmill work?
Wind is the air in motion. Energy in wind is
converted into rotary mechanical energy by wind
mills.
When blowing wind strikes the blades of a
windmill, it exerts a force on them due to which
the blades of the wind mill start rotating. This
rotary mechanical energy can be used for
pumping water, grinding flour and driving
generators to produce electricity.

Advantages of wind energy
• It is clean and pollution free source of energy.
• It is economically competitive.
• It is a very useful source in rural and remote areas where
other sources of energy are not available.

Limitations of wind energy
• Wind has a very low energy density.
• Wind energy farms should be established only at
those places where wind blows for a greater part
of a year.
• Direction of wind changes and is never the same.
• Wind farms require flat, vacant land free from
forests.
• The wind speed should be higher than 15 Km/h to
maintain the required speed of the turbine.

Geothermal energy
Internal heat energy of the earth, e.g.,
volcanoes, geysers, hot springs and
fumaroles are all sources of geothermal
energy.

How is geothermal energy
made?
• Due to geological changes, molten rocks formed in the
deeper hot regions of the earth’s crust are pushed
upward and trapped in certain regions called hot spots.
• When underground water comes in contact with the
hot spot, steam is generated.
• Sometimes hot water from that region finds outlets at
the surface. Such outlets are known as hot springs.
• The steam trapped in the rocks is routed through a
pipe to a turbine and used to generate electricity.

Nuclear energy
How is nuclear energy generated?
• In a process called nuclear fission, the nucleus of
a heavy atom (such as uranium, plutonium or
thorium) when bombarded with low-energy
neutrons, can be split apart into lighter nuclei.
• When this is done, a tremendous amount of
energy is released if the mass of the original
nucleus is just a little more than the sum of the
masses of the individual products.
• The released energy can be used to produce
steam and further generate electricity.

Advantages of nuclear
energy
• To produce a certain amount of energy, a
small amount of fuel is required.
• In a nuclear power plant, the nuclear fuel
supplies energy over a long span of time.

Limitations of nuclear
energy
• The major hazard of nuclear power generation is
the storage and disposal of spent or used fuels-the
uranium still decaying into harmful particles
(radiations).
• Improper nuclear waste storage and disposal result
in environmental contamination.
•Further there is a risk of accidental leakage of
nuclear radiation.
•The high cost o installation of a nuclear power
plant, high risk of environmental contamination
and limited availability of uranium makes large
scale use of nuclear energy prohibitive.

Requirement for alternative
or non conventional sources
of energy
• As our demand for energy is increasing day by day.
• Conventional sources of energy cause pollution
whereas non conventional sources of energy are
pollution free.
• Conventional sources of energy are exhaustible
whereas non conventional sources of energy are in-
exhaustible.

Done By, J.Bhavana
Class-XA
Roll No-5

Sources of energy

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Sources of energy