Sources of Energy- Introductions, Types, Sources Available and Much More

Energy is the basic requirement to fulfil the needs of modern life. The source of energy is basically nature. There are large and widespread sources of energy in nature, but we have not been able to utilise all the sources as yet.

Only those sources are being used which can be easily converted into useful forms of energy, such as coal, oil, gas etc. The energy of these sources is first converted into electrical energy which is utilized for human needs.

These sources are available in nature in limitation which shall exhaust in due course of time.

Hey, Welcome to Engineers Rail– The number one portal for engineering Articles and knowledge. Today, I am going deep into these energy sources in a simple and easy-to-understand manner.

I hope, you will stay with me and scroll gently to get more benefits from this article. I will start with the basic definition first.

So, without further delays, Let’s dive in-

Sources of Energy

What is Energy?

The energy may be defined as the “Capacity to do work”. We know that work is done by the application of force. Therefore mechanical energy is equal to work done which changes the position and velocity of the body.

Energy is generally measured in terms of units of work.

Law of Conservation of Energy: It states that “Energy can neither be created nor destroyed, though it can be transferred from one form to any other form, in which the energy can exist.” Therefore the total sum of energy in the universe is always constant.

Basically, energy is possessed by the materials available in nature. We simply change the form of energy and use it as per our requirements. For example, heat energy can be transformed into mechanical energy, by burning fuel in the engine.

Similarly, mechanical energy can be transformed into electrical energy with the help of an electric generator. Thereby electrical energy can be transformed into light energy, mechanical energy, sound energy, heat energy etc.

Sources of Energy-

America, a developed country, all alone, consumes 30% of the available energy in the whole world, whereas its population is only 7% of the world’s population.

Japan, Russia, America and European developed countries consume almost 70% of the world’s total fuel and the remaining fuel is consumed by three of fourth countries of the world.

So the need of the hour is that man should explore other useful sources of energy and make use of them for society.

Various sources of energy can be classified into two groups:

  • On the basis of availability
  • On the basis of the use

On the basis of Availability-

 According to availability, sources of energy can be divided into two forms:

  1. Natural Sources
  2. Artificial Sources

1. Natural Sources-

Wood, coal, gas etc. are the natural sources of energy which are used to fulfil the requirements of energy.

2. Artificial Sources-

Petrol, diesel, kerosene oil etc. are the artificial sources of energy which are produced by man.

On the basis of the Use –

According to use, the energy sources can be classified into two categories:

  1. Conventional Sources of energy
  2. Non-Conventional Sources of Energy

1. Conventional Sources of energy-

Conventional Energy Sources or Commercial Energy Sources are those sources which are being used for a long time, like wood, coal, gas etc. These sources are known as fossil fuel sources.

These sources (fuels) when burnt, give their energy which is converted into useful forms by different devices. These sources have limited stock in nature. 

2. Non-Conventional Sources of Energy-

Non-conventional energy sources are Solar energy, Tidal energy, Wind energy, Bio-gas energy etc, which have come into use in the last few years.

These are endless resources of energy. Out of these, solar energy and wind energy are two such sources which will last for an indefinite time to fulfil the needs of energy to human beings.

In India, the production of non-conventional energy is about 500 MW. The target of Govt. of India is to increase it up to 15000 MW.


The main energy sources or main source of energy available in nature are:

  1. Fossil Fuel
  2. Thermal Energy
  3. Hydro Energy
  4. Tidal Energy.
  5. Wind Energy.
  6. Solar Energy.
  7. Geothermal Energy.
  8. Nuclear Energy
  9. Biomass Energy.

Now, let’s discuss these energy sources one by one-

1. Fossil Fuel-

Fossil fuels are obtained from underneath the earth. These are produced by the deposition of biological matter such as trees, plants, animals etc. under the earth for thousands of years.

These biological matters remained hurried under the earth with pressure and temperature acting on them and converted into coal, oil and gas etc.

Fossil coal was produced beneath the earth by the action of temperature and pressure, over a long period of time due to the carbonisation of matter. Whereas, liquid fuel was produced underneath the sea bed by the decomposition of vegetation and sea animals.

Natural gas was also produced in similar conditions as liquid fuel. Coal, oil and gas obtained from underneath the earth contain hydrogen and carbon as the main constituents.

By burning these fuels, heat is produced which can be called “Fossil Energy”. These fossil fuels are dug from under the earth from mines and wells. Thereafter they pass through many processes to take commercial and usable forms.

Fig.- Conversion of fossil fuel Energy into Electric Energy:

conversation of fossil fuel into electric energy

Uses of Fossil Fuels-

These fuels are used for running:

  •  Internal combustion engines
  • Automobile engines
  • Aeroplanes
  • Rail engines
  • Trucks
  • Scooters
  • Motor-cycles

2. Thermal Energy-

Fossil fuels when burnt give away heat energy known as thermal energy. The burning of fuel is above in boilers or furnaces, thus producing steam which is used in engines and turbines to convert heat energy into mechanical energy.

This mechanical energy is used in electric generators to produce electrical energy. The conversion of fossil fuel energy into electrical energy.

Fossil energy is obtained from fossil fuels by burning them in thermal power plants. Coal is the main fossil fuel.

3. Hydro Energy-

Hydro energy is the major source of energy in the world. Water contains three types of energy- i.e., static energy, pressure energy and kinetic energy.

The energy of water is used to run water turbines where it is converted into mechanical energy. This energy is used in electrical generators which convert it into electrical energy.

Conversion of hydro-energy into electrical energy:

To convert hydro-energy into electrical energy. we first select places where water flows from a higher level to a lower level.

The water from rain, canals and rivers is stored at some suitable high level and such a place known as a catchment area or Reservoir. From this height, water flows into the turbine blades through the penstock.

Thus static energy of water is converted into mechanical energy through turbines and mechanical energy to electrical energy through electric generators.

The electrical energy thus obtained is carried to the place of use by means of electric wires.

Fig.- Conversion of Hydro-Energy into Electric Energy:


hydro energy conversation into electric energy

4. Tidal Energy-

Tide is the periodic rise and fall of the water level of the sea. Tides occur due to the attraction of seawater by the moon. These Tides can be used to produce electrical power which is known as tidal power.

Tidal energy is developed due to high tides which rise high in the sea during the moonlight. During the rest of the time, only low tides are available.

The difference in level between high tide and low tide should not be less than 5 metres in order to produce electric power.

Conversion of tidal energy into electrical energy: 

To convert tidal energy into electrical energy catchment areas are formed at suitable places in the hays of the sea. These catchment areas are connected to the sea through narrow passages.

These narrow passages are joined with controlling gates which allow seawater to enter the turbines. When the tide rises high in the sea the water enters the turbine to run it and passes to enter the catchment area.

During low tide water returns from the catchment area to the sea, passing through the turbine and running the turbine again.

Thus during high tide and low tide, the static energy of water is converted into mechanical energy. This mechanical energy is then used to run water turbines and electric power is produced.

Fig. Conversion of tidal energy into electrical energy:

Conversion of tidal Energy into Electric Energy

 If tidal energy is extracted properly, then a big part of the requirement of electric energy can be fulfilled for the whole world.

For the first time, a power station with a capacity of 240 M W was established in France at the site of the Reins River.

In India tidal energy electric houses have been established at the Bay of Kutch, Bay of Cambay Bay of Khambat, Diamond Harbour and Ganga Sagar (Hoogli river).

Here are some Advantages and Limitations of Tidal Energy:

Advantages of Tidal Energy-

  • Electric energy is available at a cheap cost.
  • Bigger electric houses can be built by enhancing catchment areas.
  • This energy is infinite
  • Complicated pieces of equipment and modern techniques are not required.
  • It is free from pollution as it does not use any fuel.

Disadvantages of Tidal Energy-

  • Such electric houses can only be constructed at the seashore.
  • The gravity of tides and their times of action at the shore are uncertain.
  • Sedimentation and Filtration of the basins are some of the added problems with tidal power plants.

5. Wind Energy-

Wind energy can be converted into mechanical energy by suitable means and its use can be made to produce electric power,

At present Denmark, the Netherlands and other European countries are using this energy as the main source of power.

 One windmill which has a 3 m size of wing diameter and 4 m height and works at 10 to 12 km/hour wind velocity has a maximum of 16% to 20% efficiency.

Such a windmill will produce 0.11 kW power at a speed of 12 km/hour. The most important factor regarding windmill is that it needs less maintenance and their expenditure is almost nil.

A windmill has a life span of about 20 yrs.

Conversion of wind energy into electric energy:

To convert wind energy into electrical energy, windmills are used. In a windmill, there are wings supported at the end of a shaft in a vertical position or horizontal position.

The blowing wind strikes the wings which move with a rotary motion, converting the wind energy into mechanical energy, which is used to run the electric generator, thus producing electric energy.

The changing direction of the wind and its intensity cause fluctuations in the voltage and frequency of the current.

To stabilise voltage and frequency windmill is made to run at a constant speed with the help of proper mechanical devices or electronic devices.

This problem can be solved by some other means also such as:

  • Collecting wind energy in electric batteries. 
  • Using flywheel to stabilise speed.
  • Converting mechanical energy into chemical energy.
  • Collecting water at a suitable height.

This last method is very effective in that windmill pumps the water by means of water pumps to a height where catchment areas are built to store water.

This water, stored in catchment areas, is used to run water turbines, thus converting the static energy of water into mechanical energy.

The mechanical energy of turbines is used to run electric generators thereby producing electric power.

Fig. Conversion of Wind energy into electrical energy:

Conversion of wind energy into electrical energy:

Here are some Advantages and Limitations of wind Energy:

Advantages of Wind Energy-

  • Wind Energy is free and inexhaustible
  • It doesn’t need transportation.
  • The wind power plant does not take a long time to construct.
  • Windmills are highly desirable and economical in rural areas which are far remote places from existing grids.

Disadvantages of Wind Energy-

  • The major disadvantage associated with wind power is that it is not consistent and steady which makes complications in designing the whole plant.
  • Special and costly designs and controls are always required.

6. Solar Energy-

Sun is a big storehouse of energy. Sun is at a distance of 1.5 x 10″ km from the Earth and carries 1.48 x 10 kJ of energy.

This heat energy reaches the surface of the earth in the form of electromagnetic radiation or waves of about 0.25 to 3 μ wavelength.

About half of this radiation is visible as light and the rest is infrared which accounts for heat Solar energy reaching the earth is of such huge value that in a few days of time, it can meet all the demands of power at earth without exhausting forever.

This energy reaches the earth per square meter the area is about 1.12 kW. This infinite amount of energy which reaches earth, only 1% of it, has been utilised by man.

Some of the hurdles behind the un-utilisation of solar energy are listed below:

  • Due to the changing angular positions of the sun, its energy intensity also changes at particular points.
  • This energy is available during the day hours and in the rainy season, its value is much less.

Conversion of solar energy into electrical energy:

Solar energy can be made usable by the following methods:

  • Glass lens method
  • Reflector method

In both the above methods solar rays are focussed at the focal point, thereby producing intense heat. This heat is utilised in the solar boilers to produce steam by heating water stored in the boiler.

The engine or turbine is run by steam to convert heat energy into mechanical energy. Thereafter mechanical energy is utilised to run the electric generator, thus producing electric power.

The conversion of solar energy into electric power Gases like Helium can be heated directly by the heat of the Sun and used to operate a gas turbine to get Electrical Energy.

In comparison to the glass lens method, the reflector method is simple, because the reflector has a simple construction and can be tilted according to the orientation of the sun.

Fig. Conversion of Solar energy into electrical energy:

Conversion of solar energy into electrical energy

Conversion of solar energy directly to electrical energy:

Solar energy can be converted to electrical energy by silicon photocells. In these cells, a silicon semiconductor is used whose efficiency is about 12%. These are mainly used in satellites because they have high costs.

The solar battery used in satellites is also made on the same principles, which stores solar energy during sunlight and uses its stored energy at night.

Photons from the sun when striking the semiconductor, they are absorbed as light energy, thereby forming free electrons having high energy.

These free electrons come out as electric current after being excited in an electric field. In solar cells, there are materials of different electric properties in the form of a junction which provides an electric field.

The main semiconductor materials are silicon, cadmium sulphide and cuprous-sulphide etc.

Uses of Solar Energy-

 Solar energy as compared to other types of energy is not being used properly and effectively for the benefit of society because of its high cost.

However, some advanced countries of the world, like Japan, Germany, America, Israel, Australia etc. are using solar energy in heating water to be used as hot water required in offices, houses etc.

Experiments are being carried out in the field of automobiles, aero-engines etc. to run them with solar energy.

Some of the prominent uses of solar energy are:

  • To heat up houses, hotels, hospitals, offices etc.
  • To supply hot water for domestic and commercial use by using solar water heaters. 
  • To use as a solar-convection drier in the paper, tea and milk industry.
  • To protect food grains and vegetables in cold storage.
  • Solar cooker, solar refrigerator, solar pimp, etc
  • To produce electric power from solar batteries in vital areas
  • Telecommunication and television broadcasting.
  • To use solar energy in salt water purification for converting it into drinking.
  • To establish solar powerhouses of capacity 20 kW to 500 kW in rural areas.

Some Important Equipment Based on Solar Energy-

Here are some most used equipment powered by solar energy:

  1. Solar Cooker
  2. Solar Pump
  3. Solar Light System
  4. Solar Water Heater
  5. Solar Inverter
  6. Solar Power Plant
I. Solar Cooker-

Solar Cooker is a device which works on solar energy. It is used to cook dal, vegetables, rice etc. It can cook four items at a time in two hours of sunlight.

The outer case of the solar cooker is made of sheet metal, wood or fibre. There is a plain mirror fitted on the lid.

The box is painted from the inner walls with black paint so that its walls absorb maximum heat. Sun rays enter the box by reflection through the plain mirror and heat up the food pots kept there.

The biggest advantage of solar cookers is that boiling pulses etc. is done at a slow speed so that its vitamins are not lost and the cost of cooking is negligible.

We can only boil the items of cooking in a solar cooker, but not bake them.

solar cooker

II. Solar Pumps-

Solar pumps of the capacity of 0.7 kW to 3.5 kW Box are available in the market. For the working of solar pumps, a voltaic cell panel is used which converts the heat energy of the sun into electric energy.

Several voltaic cells are connected in series. The electric energy is converted into mechanical energy to run the solar pumps. Solar pumps can feed water to a small village for irrigation purposes and to provide drinking water.

III. Solar Light Systems-

In this system heat energy, received through sun rays, is converted into electric energy by means of voltaic cells. This electric energy is used to charge storage batteries.

Once they are charged, they can be used to lighten the tube lights, fans, bulbs etc.

IV. Solar Water Heater-

This heater is used to supply hot water in hotels, homes, commercial establishments etc. This is available in a capacity of 100 litres to 500 litres.

It can heat the water upto 60°C to 80°C. Its operation, as well as maintenance cost, is negligible.

V. Solar Inverter-

There are several companies who are preparing to launch such inverters in the market which can utilise solar energy to charge batteries.

The charged batteries shall be used for domestic purposes in running the inverters.

VI. Solar Power Plants-

 A cluster of solar panels is constructed to convert solar energy into electric energy. This energy is then used to charge batteries.

Then electric energy from the batteries is converted into three phase supply and used to run tube wells and electric motors etc.

7. Geo-Thermal Energy-

We know that several million years before the earth was formed. The earth was like a big ball of fire and slowly it was cooled in due course of time to form a solid and hard crust.

On the surface of the earth, the growth of vegetation, trees and plants etc took place slowly but the internal surface of the earth remained extremely hot whose temperatures ranging from 3000°C to 4000°C.

Apart from this, the earth contains some metals of unstable atoms like uranium and thorium which disintegrate and lose their energy to produce heat. Such metals are called radioactive elements. This heat energy stored on earth is the source of geothermal energy.

Examples of geothermal energy are hot gasses and steam. hot water streams, wells, etc coming up at different places of the earth which are used to produce electric power or any other useful purpose.

Conversion of Geo-thermal energy into electric energy:

Geothermal energy is obtained from. beneath the earth by digging deep wells at proper places. The hot water that comes out of the wells is sent to boilers to convert it into steam.

In some places, hot gases or steam is found from the deep wells of the earth which are sent to steam turbines to convert heat energy into mechanical energy. Thereafter mechanical energy is converted to electric energy through electric generators.

Fig. Conversion of Geo-thermal energy into electrical energy:

conversion of geo thermal energy into electrical energy:

Advantages of Geo-Thermal Energy-

  • Cheap
  • Does not pollute the atmosphere

Disadvantages of Geo-Thermal Energy-

  • High cost
  • Uncertain Energy

8. Nuclear Energy-

The nuclear energy source is such an energy source which consumes in little quantity of fuel to give out a large amount of energy.

This energy is obtained by the dissociation of the uranium atoms. We know that every atom is composed of one nucleus and one or more electrons.

In the nucleus, there are fixed particles neutrons and protons. The mass of the nucleus is less than the combined mass of neutrons and protons.

This difference of mass is equivalent to that energy which was released during the formation of the nucleus. When a nucleus is broken, then the same amount of energy has to be given to it from outside.

This energy difference is called binding energy. During nuclear reactions, this energy is obtained in the form of nuclear energy.

The evolution of nuclear energy is due to nuclear reactions.

The main nuclear reactions are:

  • Nuclear fusions
  • Nuclear fission

Nuclear fusion:

In the process of nuclear fusion, two light nuclei combine together to form a heavy nucleus and energy is emitted. This process is practically not possible as yet because it needs a temperature as high as a few lacs of degrees which is impossible to create and maintain.

Nuclear Fission:

In the process of nuclear fission one heavy unstable nucleus is broken into two equal nucleus of almost equal weights. During the process, a large amount of energy is liberated.

When the dissociation of the nucleus is done under controlled conditions then an infinite amount of energy is liberated and is used to run heavy power-houses. 

Conversion of Nuclear Energy Into Electric Power:

This process consists of nuclear fission of uranium in which a free neutron is made to enter an unstable nucleus with a slow speed, thereby breaking the nucleus into two parts of approximately equal mass, with the result that infinite energy is released.

The speed of neutrons is very high, which is slowed down by a moderator. The moderators generally used are graphite, heavy water, and Bariluim. Helium gas etc.

This slow-speed neutron is again broken into an unstable nucleus, thus creating a chain reaction which continues and energy is received constantly.

The nuclear Reactor is the main part of a Nuclear Power Plant. Nuclear fuel (U25 in general) is dissipated in this reactor by the chain reaction.

The heat energy obtained during the chain reaction is given to a boiler or heat exchanger through a medium which may be liquid, gas or mercury.

Thus water is heated to form steam to run the turbine. The heat energy of steam is converted to mechanical energy by the turbine and used to run the electric generator for the production of electric power.

Fig. Conversion of Nuclear energy into electrical energy:

Conversion of Nuclear energy into electrical energy

Main parts of a Nuclear Reactor-

  • Fuel, which is stored in the Reactor in the form of core
  • Reflector
  • Moderator
  • Control Rods
  • Coolant
  • Radiations shield
  • Measuring System

Fig.- Nuclear Reactor-

nuclear reactor

Main Elements of Nuclear Power Plant-

  • Nuclear Reactor
  • Heat Exchanger
  • Steam Turbine
  • Condenser
  • Electric Generator
  • Pumps

Uses of Nuclear Energy-

  • Nuclear energy is used in the following areas:
  • Medicals and agriculture areas
  • Electric power generation in industrial areas.
  • Peaceful works like nuclear explosions in the field of digging lakes, dams, mines, ponds etc.
  • Bomb explosions in wartime

9. Biomass Energy-

The biological materials obtained from oceans, lakes, ponds, crops, trees etc. are called Biomass. It is a non-conventional source of energy.

Apart from this rice husk from rice fields, sugar-cane husks, shins of ground-nuts, corn-husk, domestic waste, cow dung etc, are also part of bio-mass materials.

These materials are such that they absorb energy from the sun and store it in themself. When they are burnt, they return that energy in the form of heat energy.

All the vegetations existing in nature are in the form of biomass.

These are mainly of two types:

  • Biomass of land-vegetation
  • Biomass of water-vegetation

Biomass of land vegetation are tree barks, leaves, plants, and bushes etc, whereas bio-mass of water vegetation are plants, bushes etc, growing underwater.

Conversion of Biomass into Electric Power:

The green part of leaves (chlorophyll) absorbs sun rays and reacts with CO2 and H2O to form atomic oxygen and hydrogen, the carbon content is separated and creates bio-mass by the process of photosynthesis.

Thus biomass is a form of solar energy. Heat energy is obtained by the direct burning of biomass. Apart from this, the fermentation and digestion processes give oil, ethanol and methane from biomass.

Hydro gasification process produces methanol and gasoline from biomass.

Biogas energy: It is a non-conventional source of energy, India is an agricultural-based country and this source of energy is very important because a large number of farmers do cattle farming. Gobar gas can be easily obtained from cattle waste which is a popular means of fuel gas.

The main components of biogas plants-

  • Dome
  • Foundation
  • Digester
  • Inlet
  • Outlet
  • Gas pipe

For the production of biogas, a fixed dome Janta-type model plant. It is constructed underneath the earth by a brick structure bound by cement and sand.

A digester is the central part of the plant. On one side of the digester, there is an inlet passage and on the other side, there is an outlet passage.

On top of the digester, there is a dome made of a thick sheet of tin. A pipe is fitted on the dome to take out the gas. To start the plant the stale dong and water in proper proportion are put in a tank from when it reaches the digester through the inlet passage.

This mixture produces gas in the form of bubbles which are collected in the dome. It can be taken out by means of a tap valve and sent to the place where it is to be used.

Uses of Biogas-

This gas is used in gas burners for cooking purposes, thereby saving fuel. The remaining dung is good-quality manure and can be used in crops. Biogas can also be used in lanterns to provide light.

Advantages of Biogas-

This gas is cheap and does not cause pollution.

Disadvantages of Biogas-

The important limitation is that with a large quantity of bio-mass, less energy is obtained. A lot of ash and waste materials are left which creates the problem of their disposal.

Its real use can be economical only at the place where it grows. Its transportation is also very difficult and costly.


Wrapping Up-

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You might find the following recommended articles interesting to read further:

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Gaseous Fuels: Definition, Classifications, Examples, Advantages

Classification of Coal: The Ultimate Guide You Will Never Read


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