1. What is Source of Energy?

Notes added by teacher Sudhanshu in Batch 1 for Test 1



Unit V Natural Resources > Chapter 1 Sources of energy > Different forms of energy

1. What is Source of Energy?

Chapter 14

Sources of Energy

A source of energy is that which is capable of providing enough useful energy at a steady rate over a long period of time.
The largest source of energy on land is sunlight. There are different purposes for which energy is needed such as for food, for lightning, transport, running machines etc.

A good source of energy should be-

  • Cheap and easily available.
  • Safe in handling and use.
  • Do not cause any environment pollution.
  • Easy to store and transport.

Characteristics of a good fuel

  • High calorific value.
  • Less smoke.
  • Less residue after burning.
  • Easy availability.
  • Inexpensive.
  • Easy to store and transport.

Classification of Sources of energy
The sources of energy can be classified as follows:

  1. Renewable sources of energy.
  2. Non-Renewable sources of energy.

1. Renewable sources of energy: Renewable sources of energy are those which are inexhaustible, i.e., which can be replaced as we use them and can be used to produce energy again and again.
These are available in an unlimited amount in nature and develop within a relatively short period of time.
Example of Renewable Sources of Energy:

  • Solar energy.
  • Wind energy.
  • Water energy (hydro-energy).
  • Geothermal energy.
  • Ocean energy.
  • Biomass energy (firewood, animal dung and biodegradable waste from cities and crop residues constitute biomass).

Advantages of Renewable Sources of Energy

  • These sources will last as long as the Earth receives light from the sun.
  • These sources are freely available in nature.
  • These sources do not cause any pollution.

2. Non-Renewable Source of Energy: Non-renewable sources of energy are those which are exhaustible and cannot be replaced once they have been used. These sources have been accumulated in nature over a very long period of millions of years.
Examples of Non-renewable Sources of Energy:

  • Coal.
  • Oil.
  • Natural gas.
    All these fuels are called fossil fuels.

Disadvantages of Non-renewable Sources of Energy

  • Due to their extensive use, these sources are fast depleting.
  • It is difficult to discover and exploit new deposits of these sources.
  • These sources are a major cause of environmental pollution.

Types of Sources of Energy

There are two types of Sources of Energy –

  • Conventional Sources of Energy - include the fossil fuels such as coal and petroleum.
  •  Non-conventional Sources of Energy - include solar cooker, solar cell panel etc.

Conventional Sources of Energy
Fossil Fuels:  

  • Fossil fuels are the remains of prehistoric plants and animals which got buried deep inside the early millions of years ago due to some natural processes.
  • These fossil fuels are non-renewable sources of energy.
  • They cause environmental problems due to pollution.

Formation of Fossil Fuels:

  • During its formation, an entire organism or its parts often get buried in sand or mud.
  • These, then decay and disintegrate leaving no signs of their existence.
  •  In fact, the harder parts of organisms after their death settle down and are covered by sediments and subjected to extreme pressure and temperature or the Earth converts them into fossil fuels, the process being referred to as fossilization.

Disadvantage of Fossil Fuels

  • The fossils are non-renewable sources of energy and once used cannot be renewed.
  • Burning of fossil fuels causes air pollution.
  • These fuels cause pollution. They release different oxides which causes acid rain which damages plants, animals, houses etc.
  • Excessive release of carbon-dioxide also causes global warming.
  • The fossil fuels reserves in the Earth are limited and may get exhausted soon.

Thermal Power Plants

  • Thermal power plant is used to generate electricity using heat.
  • Burning of fossil fuels produces the steam which is used to run the turbines.
  • This method helps in efficient transmission of electricity.

Hydro Power Plants

  • Use to convert potential energy of falling water into electricity.
  • They are associated with dams.
  •  They do not cause any pollution.
  • Dam construction also prevents flooding of rivers and also provide water for irrigation.

Advantages of Hydro Power Plant:

  • It is readily and abundantly available everywhere free of cost.
  • It is eco-friendly and does not produce any kind of environmental pollution.
  • It is a renewable source as water itself is a renewable and inexhaustible resource.
  • It is a cheap source of energy, as it does not involve any costly investment.

Disadvantages of Hydro Power Plant

  • Highly expensive to construct.
  • Dams cannot be constructed on all river sites.
  • Large areas of human habitation and agriculture fields get submerged.
  • People face social and environmental problems.

Conventional Sources of Energy using technology

Bio-Mass: Biomass is defined as living matter or its residue and is a renewable sources of energy. The dead remains of plants and animals is known as Biomass.
The biomass includes.

  • all the new plant growth
  • Agriculture and forest residues (like Bio-gases, dark, sea dust, wood savings, roots, animals dropping, etc.),
  • Carbonaceous wastes (like sewage, garbage, night-soil, etc.)
  • Biodegradable organic effluent from industries.

It is the source of the conventionally used fuels that are used in our country. For example; Cow dung cakes, fire-wood, coal, charcoal etc.
Bio-gas: It is a mixture of gases produced during decomposition of bio mass in the absence of oxygen. (Anaerobic Respiration). Methane is the major component of bio-gas.
Bio-gas plants: Animal dung, sewage, crop residues, vegetable wastes, poultry dropping, etc. are used to produce Bio-gas in Bio-gas plants.

Advantage of Bio-gas

  • A Bio-gas plant, is quite simple, can easily be built in rural areas. A small plant using dung from 3 to 4 heads of cattle is capable of supplying Bio-gas for 6 hours daily for cooking purposes.
  • Bio-gas is a clean fuel that burns without smoke and leaves no ash.
  • The main constituent of Bio-gas, i.e., ethane has a higher calorific value (55 kj/g) that of petrol (50kj/g).
  • The spent slurry, being rich in nitrogen and phosphorus is good manure.
  • By using Bio-gas, firewood is saved and deforestation is reduced.

Composition of Bio-gas: Bio-gas is mainly composed of methane (up to 75%), C02 (25%) and traces of other gases such as nitrogen and hydrogen. Whereas methane is a high-value calorific fuel, carbon dioxide is an inert gas.
Wind Energy: When large masses of air move from one place to another then it is referred to as wind. During this process, kinetic energy gets associated with it which is referred to as wind energy.
It can be converted into mechanical and electrical energy.
Kinetic energy of wind is used in running of windmills, which are used to lift water, grind grains etc.

Uses of Wind Energy
The important uses of wind energy are:

  • It is used to drive windmills, water lifting pumps, and flour mills, etc.
  • It is used to propel sail boats.
  • It is used to fly engine fewer airplanes or gilders in the air.
  • It is used to generate electrically used for various purposes like lightning, heating, etc.


  • Eco-friendly
  • Renewable.


  • Wind speed does not uniform always.
  • Needs a large area to erect series of windmills.
  • Big amount of investment is needed.
  • The output is less as compared to investment.

2. Non-Conventional Sources of Energy

Notes added by teacher sudhanshu@kaysonseducation.co.in for Batch Combined

Unit V Natural Resources > Chapter 1 Sources of energy > Conventional and non-conventional sources of energy.

2. Non-Conventional Sources of Energy

Non-Conventional Sources of Energy     

Solar Energy: 

  • The sun is the main source of energy for all living beings on this earth.
  • The energy produced by the sun in the form of heat and light energy is called as solar energy.
  • Solar radiations can be converted electricity through solar cells (Photovoltaic cells).
  • Photovoltaic cells convert solar radiations directly into electricity through silicon solar cells.
  • Solar cells arrange on a large flat sheets form a Mirror solar panel.
  • Solar cookers are painted black from outside and a large glass plate to trap solar radiations by greenhouse effect.

Solar Cooker: 

  • Solar cooker is very simple in design and mode of function.   
  • It is usually made from mirrors.
  • Plain mirrors are placed inside a rectangular box.
  • The light reflected from the plain mirrors concentrates the solar energy inside the solar cooker which generates enough heat to cook food.

Advantages of Solar Cookers

  • Eco-friendly.
  • Renewable.
  • Used in rural areas.
  • Retains all the nutrients in food due to slow cooking.

Disadvantage of Solar Cookers:

  • Silicon cells are expensive.
  • Solar radiations are not uniform over the Earth’s surface.
  • Cannot be used at night or on cloudy days.
  • Cannot be used to make chapattis, for frying as these require a temperature of 140 °C or more. (Maximum temperature of 100 °C only can be achieved in a solar cooker) Other Solar Devices are solar water heater and Solar furnace.

 Solar Panel

  • Solar panel is an assembly of photo -voltaic cells mounted in a framework for installation.
  • Solar panels use sunlight as a source of energy to generate direct current  electricity.
  •  A collection of PV modules is called a PV panel, and a system of PV panels is called an array.
  •  Arrays of a photovoltaic system supply solar electricity to electrical equipment.

Energy from Sea

Tidal Energy: Due to the gravitational pull of the moon, tides happen near seashores. Water rushes up near the seashore during high tide and goes down during low tide. Dams are built near seashores to collect the water which comes during a high tide. When the water runs back to the ocean, the flow of water can be utilized to generate electricity.
Wave Energy: Waves can also be a good source of energy. Many devices are being designed and tested to produce wave energy. For example; a hollow tower is built near the seashore. When water gushes in the tube because of wave, it forces the air upwards. The kinetic energy of air in the tube is used to run a turbine. When the wave goes down; air from up goes down the tube which is also used in running the turbine.

Ocean Thermal Energy: The water at sea surface is hot during the daytime, while the water at a lower level is cold. The temperature differential in water levels can be utilized to generate energy. If the temperature differential is more than 20°C, then ocean thermal energy can be utilized from that place. For this, a volatile liquid; like ammonia; is boiled using the heat from the hot water at the surface. The steam of the volatile liquid is utilized to run the turbine to generate electricity. Colder water from the surface below is utilized to condense ammonia vapour which is then channelized to the surface to repeat the cycle.
Geothermal Energy: Heat energy from molten rocks present inside the earth created under certain favorable conditions by natural processes is called geothermal energy. It is the only type of energy which does not use solar energy.

Magma is formed when this heat melts the rocks. The rocks and hot gases are called magma.
The magma gets collected at some depths below the Earth’s surface. These places are called ‘Hot spots’.
When underground water comes in contact these hot spots, it changes into steam, which can be used to generate electricity.

Advantages of Geo Thermal Energy

  • renewable
  • Inexpensive

Disadvantages of Geo Thermal Energy

  • Only a few sites are available for harnessing energy.
  • Expensive

 Nuclear Energy:

  • Nuclear fission is the process during which a bigger nucleus breaks to produce two smaller nuclei.
  • The process generates a huge amount of energy.
  • This phenomenon is utilized in nuclear power plants.
  •  Nuclear power is safest for the environment but the risk of damage due to accidental leaks of radiation is pretty high.
  • There are two distinct ways of obtaining nuclear energy, (a) Nuclear fission and (b) Nuclear fusion.

Advantages of nuclear energy.
A very large amount of energy can be produced by a nuclear process on using very small amount of nuclear fuel in a nuclear reactor.
The energy so produced can be easily transformed into electrical energy.
It does not produce harmful gases.

Disadvantages of Nuclear Energy:

  • Risk of nuclear waste leakage.
  • High cost of setting up of nuclear plant.
  • Pollution of environment.

 Difference between Nuclear Fission and Fusion

Environmental consequences of the increasing demand for energy:

  • The combustion for fossil fuels produces acid rain and damages plants (crops), soil and aquatic life.
  • The burning of fossil fuels is increasing the amount of greenhouse gas, carbon dioxide in the atmosphere.
  • The construction of hydropower plants is a disturbing ecological balance.
  • Nuclear power plants are increasing radioactivity in the environment.