What Are the Sources of Electricity?

In the last article I explained how electricity is generated. In this article I will tell you about the various sources of electricity and their pros/cons.

The various sources of electricity are:

Hydro: Hydro power plants work in conjunction with dams that hold back water, thus creating a reservoir. A turbine is located at a lower level with respect to the reservoir. When water is released from the dam, it flows under the effect of gravity, thus converting its potential energy into kinetic energy, and strikes the turbine, thus rotating it.

Coal: This is the most popular method of generating electricity. Coal is burnt to produce heat, which is used to convert water to steam, which in turn rotates the turbines. The steam is condensed back to water and recycled.

Gas: There are many gas power plants in the world. They are like coal-fired power plants except instead that gas is burnt instead of coal.

Oil: These are usually much smaller in capacity compared to coal/gas fired power plants, and are popularly called diesel generator (DG) sets. They burn diesel instead of coal/gas.

Nuclear: These are similar to coal/gas power plants except that heat is produced by nuclear fission reaction. The fuel for most nuclear plants is highly enriched uranium (U-235) which is one of the few elements that can undergo induced fission reaction when a neutron is fired into its nucleus. A pound of U-235 produces the same amount of energy as  burning a million gallons of gasoline!

Renewables: They generate electricity from renewable sources which are of many types. Tidal is like hydro in many ways, excet that it works with the ebb and flow of the sea. Geothermal uses the heat trapped deep within the earth to generate steam, while biomass/biogas refers to plants or plant-based materials which can be burned directly via combustion to produce heat or indirectly after converting it to various biofuels or biogas, but both are intrinsically similar to thermal power plants.

In concentrated solar thermal, the sun’s heat is used to generate steam and so it is also like thermal power. Wind rotates turbines and is therefore electromagnetic in nature as well. The operating principle of solar PV and fuel cells, however, is not electromagnetic in nature.

All sources of electricity that are electromagnetic in nature are different in how they rotate the turbines, which in turn the rotate the armatures.

Sources of Electricity in India



As of December 31st 2013, the various sources of electricity contributed to the total electricity generated in India as per the pie chart above.

  • Coal is the most popular source of electricity contributing 59% of the total electricity generated.
  • Hydroelectricity comes 2nd and contributes a healthy 17%.
  • Renewable energy sources contribute 12% of the total electricity generated, which is not bad at all. Wind energy contributes a large part of this as of today, however, solar is expected to overtake it in the near future.
  • Nuclear power, despite all the promise that it holds and the talk that surrounds it, contributes a meagre 2%.

The table below summarizes the cost of construction per MW, the pros/cons, and the availability of fuel for the various sources of electricity.

MethodCost of construction
(crores per MW)
Cost of Generation
(Rs. Per unit)

Hydro10+<0.251. Very low running costs

2. Environmentally friendly
1. High setup costs

2. Dependence on water & therefore limited
Coal5-61-31. Proven technology

2. Low setup & running cost
1. Very harmful to the environment
Gas6-71-31. Proven technology

2. Low setup & running cost
1. Harmful to the environment although not as much as coal
DieselRs.10,000-Rs.20,000 per kW15+1. Very low setup cost

2. Is reliable and portable
1. Very harmful to the environment
Nuclear12+<11. High setup costs

2. Very low running costs
1. Can be catastrophic in the event of an accident

2. Very high exit costs

As the table shows, each source of electricity has its own unique advantages and disadvantages. That is why there is a mix of all of them in the total electricity that we generate. However, coal dominates the energy mix by a fair distance. So I will tell you all about coal next in a mini-series of articles titled, The Black Truth.

(Prashant Karhade is a guest author of ABC of Solar)


How Is Electricity Generated?

The Black Truth: Part I

The Black Truth: Part II

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