NCERT Solutions Class 10th Science Chapter – 14 Sources of Energy Notes

Sources of Energy

1. Environmental Consequences
2. Conventional Sources
3. Good sources of Energy
4. Non Conventional Sources
5. Life of Energy Source
6. Renewable
7. Non-Renewable

Conventional Sources

1. Fossil fuel
2. Hydro power
3. Biomass
4. Wind Energy

1. Fossil fuel
(i) Coal
(ii) Natural gas
(iii) Petroleum

Non Conventional Source

1. Solar Energy
2. Geothermal Energy
3. Nuclear Energy
4. nergy from the Sea

(i) Tidal energy
(ii) Wave energy
(iii) Ocean thermal energy

Renewable Source

(i) Solar energy
(ii) Wind energy
(iii) Mechanical energy of water
(iv) Ocean energy
(v) Bio mass
(vi) Geothermal

Nonrenewable Source

(i) Coal
(ii) Petroleum
(iii) Natural gas

• Energy comes in different forms and one form can be converted into another.
• A source of energy is one which provide adequate amount of energy in a convenient form over a long period of time.

Need of energy:            

• Photosynthesis
• For cooking food
• For lightning (CFL, LED, bulb)
• For transport
• For running machines
• For industrial activities and agricultural work

Qualities of a Good Source of Energy

(i) Which would do a large amount of work per unit mass.
(ii) Cheap and easily available.
(iii) Easy to store and transport.
(iv) Safe to handle and use.
(v) Does not cause environmental pollution.

Fuels: The materials which are burnt to produce heat energy are known as fuels.
For Example wood, coal, LPG and kerosene etc.

Characteristics of a Good Fuel

• High calorific value (give more heat per unit mass).
• Burn without giving out any smoke or harmful gases.
• Proper ignition temperature.
• Cheap and easily available.
• Easy to handle, safe to transport.
• Convenient to store.
• Burn smoothly.

Sources of Energy

Conventional Sources of Energy

• Fossil fuels (Coal, Petroleum)
• Thermal power plant
• Hydro power plants
• Geothermal energy

Non-conventional Sources of Energy

• Solar energy (e.g. solar cooker, solar cell panel)
• Energy from the sea (tidal wave, OT energy)
• Biomass-biogas plant
• Wind energy
• Nuclear energy

CONVENTIONAL SOURCES OF ENERGY:

Sources of energy which are used by people.
Example: fossil fuels, bio mass, water energy, wind energy etc.

1. FOSSIL FUELS: Used in several areas.

• Fuels developed from the fossils
  e.g. coal, petroleum.
• Take millions of years to form.
• Available in very limited amount.
• These are non-renewable sources of energy.
• India has about 6% share in the world reserved coal, that may last 250 years
  more at the present rate of consumption.

Pollution Caused by Fossil Fuels

• Release oxides of carbon, nitrogen and sulphur (acidic in nature) which causes acid rain that damages trees, plants, reduces fertility of soil.
• Produces large amount of CO, in the atmosphere which causes green house effect leading to excessive heating of the earth.

Controlling Pollution Caused by Fossil Fuels

• Increasing the efficiency of the combustion process.
• Using various techniques to reduce the escape of harmful gases and ashes into the surroundings.

2. THERMAL POWER PLANT:

Heat Energy → Kinetic Energy → Turbine → Generator → Electricity

A power plant which uses heat energy to generate electricity.

• Burning of fossil fuels produces steam to run turbines.
• Set up (power plants) near the coal and oil fields to minimize the cost of transportation and production.
• Elements present in fly ash increases crop production.

• Convert the potential energy of falling water into electricity.
• Hydro power plants are associated with dams.

Around 25% of our country’s energy requirement is met by Hydro Power plants.

Advantages:

(i) No environmental pollution.
(ii) Flowing water is a renewable source of electric energy.
(iii) Construction of dams prevents flooding of rivers, provide water for irrigation, and possibility for fish farming.

Disadvantages:

(i) Large areas of agricultural land, a vast variety of flora and fauna, human settlements get submerged in the water reservoir formed by the dam.
(ii) Large ecosystems are destroyed.
(iii) Vegetation that submerge under water rots in anaerobic conditions and produces large amount of methane which is a green house gas.
(iv) Creates the problems of satisfactory rehabilitation of displaced people.

Improvements in the Technology for Using Conventional Sources of Energy

1. BIOMASS:

The dead parts of plants and trees and the waste materials of animals and man is called Biomass.

(1) Wood: It is a biomass and used as a fuel since long time.

Disadvantages:

• Produces a lot of smoke on burning which is harmful for health and environment.
• Do not produce much heat.
• Thus by improvement in technology we can improve the efficiency of traditional sources of energy.

For Example: wood can be converted into better fuel called charcoal.

(2) Charcoal: 

When wood is burnt in limited supply of air, then water and other volatile materials gets removed and charcoal is formed.

Wood Limited Supply of O₂ → Charcoal

Charcoal is better fuel than wood because:
(i) It has higher calorific value than wood.
(ii) It burns without producing smoke
(iii) It is a compact fuel, easy to handle and convenient to use.

• produces less heat
• produces lot of smoke.
• cowdung does not burn completely, produces lot of ash as residue.
• low calorific value.
• By making biogas (or gobar gas) from cow dung, we get a smokeless fuel.

(5) Wind energy:

• Unequal heating of the landmass and water bodies by solar radiations generate air movement and causes wind to blow.
• Kinetic energy of the wind can be used:
  (i) to generate electricity by turning the rotor of the turbine.
  (ii) to lift water from the well.
  (iii) to run the flour mills.
• But the output of a single wind mill is quite small so a number of windmills are erected over a large area called wind energy farm.
• The minimum wind speed for wind mill to serve as a source of energy is 15-20 Kmph

Advantages:

(i) Eco-friendly.
(ii) Efficient source of renewable energy.
(iii) No recurring expenses for production of electricity.

Disadvantages:

(i) Wind energy farms need large area of land.
(ii) Difficulty in getting regular wind speed of 15-20 Kmph.
(iii) Initial cost of establishing wind energy farm is very high.
(iv) High level of maintenance of blades of wind mill.

• Denmark is called the ‘Country of Winds’.
  
• India is ranked among top 10 countries in harnessing wind energy for the production of electricity.
  
• In India largest wind energy farm has been established near Kanyakumari in Tamil Nadu and it generates no less than 380 MW of electricity.

Alternate or Non-conventional Sources of Energy

Day by day, our demand for energy has increased, so there is a need for exploring other source of energy.

Reasons for alternate sources of energy

(i) Fossil fuel reserves in the earth are limited which may get exhausted soon if we use them at the current rate.
(ii) Reduce the pressure on fossil fuels making them last for a longer time.
(iii) To reduce the pollution level and to save environment.

1. SOLAR ENERGY:

Sun is the ultimate source of energy. Energy obtained from the sun is called solar energy.
Solar constant = 1.4 KJ/s/m²

Outer edge of the earth receives solar energy equal to
= 1.4 KJ/s/m² or 1.4 KW/m² [1 KJ/s = 1 KW]

Solar energy devices : Devices using solar energy are:
(i) Solar cooker
(ii) Solar water heater
(iii) Solar cells

In these Sources of energy to collect solar energy and use it in the form of heat energy

Solar heating devices :

• Use black painted surface because black surface absorbs more heat as compared to white or other surface.
• Use of glass plate because it allows infrared radiations to enter through it but does not allow the radiations to exit through it, causing more greenhouse effect that result in increase in temperature.
  

(i) SOLAR COOKER

Box Type Solar Cooker : It consists of a rectangular box which is made up of wood or plastic which is painted black.

• Inner walls of the box are painted black to increase heat absorption.
  
• Solar cookers are covered with glass plate and have mirror to focus the rays of the sun and achieve higher temperature.
  
• Temperature inside the box increases 100°C-140°C in 2-3 hours.

Advantages:

(a) Save precious fuel like coal, LPG, kerosene.
(b) Does not produce smoke.
(c) Nutrients of food do not get destroyed while cooking.

Disadvantages:

(a) Solar cookers cannot be used during night.
(b) If the day sky is covered with clouds, solar cooker cannot be used.
(c) Direction of reflector of solar cooker changes from time to time to keep it facing the sun.
(d) Cannot be used for frying or baking purposes.

2. SOLAR CELL:

• Solar cells convert solar energy into electricity.
• A solar cell develops a voltage of 0.5-1 V and can produce about 0.7 W of
  electricity.
• A large number of solar cell are combined in an arrangement called solar panel

Advantages:

(a) Have no moving parts.
(b) Require little maintenance.
(c) Can work without any focusing device.
(d) Can be set up in remote and in accessible areas.

Limitations:

(a) Manufacturing is expensive.
(b) Availability of special grade silicon for making solar cells is limited.
(c) Silver wire for interconnection of cells is expensive.

Uses of Solar Cell:

(a) Artificial satellites and space probes use solar cells as the main source of
energy.
(b) Radio, TV relay stations in remote locations use solar cell panels.
(c) Traffic signals, calculators and many toys are fitted with solar cells.

GEOTHERMAL ENERGY

• Geo’ means ‘earth’ and ‘thermal’ means ‘heat’.
• Geothermal energy is the heat energy from hot rocks present inside the earth.
• When underground water comes in contact with ‘hot spot’, steam is generated. Steam trapped in rocks is routed through pipes to a turbine and used to generate electricity.

Advantages:

(a) Economical to use geothermal energy.
(b) Does not cause any pollution.

Limitations:

(a) Geothermal energy is not available everywhere.
(b) Deep drilling in the earth to obtain geothermal energy is very difficult and
expensive.

• In New Zealand and USA, there are several power plants based on geothermal energy are operational.

NUCLEAR ENERGY

• The energy released during a nuclear reaction is called nuclear energy.
• It can be obtained by two types of nuclear reactions:

(i) Nuclear fission
(ii) Nuclear fusion

(i) Nuclear Fission:

• ‘Fission’ means split up.
• The process in which the heavy nucleus of a radioactive atom (such as uranium, plutonium or thorium) split up into smaller nuclei when bombarded with low energy neutrons, is called nuclear fission.
• A tremendous amount of energy is produced.
• U-235 is used as a fuel in nuclear reactor in form of uranium rods.

Working: In a nuclear reactor self sustaining chain reaction releases energy at a
controlled rate, which is used to produce steam and further generate electricity.

Major Nuclear Power Plants :

(a) Tarapur (Maharashtra)
(b) Rana Pratap Sagar (Rajasthan)
(c) Kalpakkam (Tamil Nadu)
(d) Narora (U. P.)
(e) Kakrapar (Gujrat)
(f) Kaiga (Karnataka)

(ii) Nuclear Fusion :

In nuclear fusion, two nuclei of light elements (like hydrogen) combine to form heavy nucleus (like helium). Enormous amount of energy is released.

Extremely high temperature and pressure is needed for fusion.
Hydrogen bomb is based on this phenomenon.
Nuclear fusion is the source of energy all the stars including sun.

Advantage:

(a) Production of large amount of useful energy from a very small amount of nuclear fuel.
(b) Does not produce green house gases like CO₂.

Limitations:

(a) Environmental contamination due to improper nuclear waste storage and its disposal.
(b) Risk of accidental leakage of harmful radiations. e.g., chernobyl accident
(c) High cost of installation.
(d) Limited availability of nuclear fuel.

Environmental Consequences

Exploiting any source of energy disturbs the environment in some way or the
other. Thus, the source we would choose depends upon following the factors:

(a) Ease of extracting energy from the source.
(b) Cost of extracting energy from the source.
(c) Efficiency of technology available to extract energy.
(d) The environmental damage caused by using that source.

In other words, no source of energy is said to be pollution free. Some source are cleaner than the other.

For example: solar cells may be pollution free but the assembly of the device
cause some environmental damage.

How Long Will an Energy Resource Last ?

Sources of Energy

(1) Non-renewable Sources of Energy: Sources that will get depleted some day.
For example: Fossil fuel

(2) Renewable Sources of Energy: Energy sources that can be regenerated and that will last for ever.
For example: Wind energy, water energy.