In the last article I talked about power theft in India, how to stop it, and Government of Gujarat’s Jyotigram Yojana. In this article I will tell you about the various sources of electricity and their pros/cons.
Before I talk about the various sources of electricity, it is necessary to understand the basic operating principle of electromagnetic generators, discovered in 1832 by Michael Faraday. The principle, now called Faraday’s law, is that an electromotive force (also referred to as EMF or potential/voltage difference) is generated in an electrical conductor which encircles a varying magnetic flux or field. EMF is also generated if an electrical conductor is rotated inside a magnetic field.
Figure 8.1 shows an elementary generator. The pole pieces provide the magnetic field. They are shaped and positioned as shown to concentrate the magnetic field as close as possible to the wire loop. The loop of wire that rotates in the magnetic field is called the armature. The ends of the armature are connected to rings called slip rings, which rotate with the armature. The brushes, usually made of carbon with wires attached to them, ride against the rings. The generated voltage appears across these brushes.
Figure 8.2 shows the voltage generated at various points during the clockwise rotation of the armature. As can be seen, this rather simple arrangement generates a single phase AC waveform. If you have 2 more armatures fixed at 120° and 240° with respect to this armature, and rotate all of them together in this magnet, you will generate a 3-phase AC waveform. While the actual size of electric generators is huge and their construction a lot more complex, their basic principle remains the same. This is how mechanical energy/motion is converted into electrical energy or electricity. The various sources of electricity are different in how they rotate the turbines, which in turn rotate the armatures.
This is the most popular method 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.
There are many gas-powered power plants in the world. They are like coa-fired power plants except that gas is burnt instead of coal.
These are usually much smaller in capacity compared to coal-fired or gas-fired power plants, and are popularly called diesel generator (DG) sets. They burn diesel instead of coal/gas.
These are similar to coal-fired or gas-fired power plants except that heat is produced by nuclear fission reaction. The fuel for 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 that burning a million gallons of gasoline does!
Hydro power plants work in conjunction with dams that hold back water, thus creating reservoirs; the turbine is located at a lower level with respect to the reservoirs. 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.
There are many different types of renewable energy sources. Tidal energy is like hydro in many ways. Geothermal energy uses the heat trapped deep within the Earth to generate steam, while biomass/biogas refer to plants or plant-based materials which can be used directly via combustion to produce heat or indirectly after converting it to various biofuels, but both are intrinsically similar to thermal power plants. In concentrated solar thermal, 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. Operating principle of solar PV and fuel cells, however, is not electromagnetic in nature. All the above-mentioned renewable energy sources will be covered in detail later in the series.
As of December 31st 2013, the various sources of electricity contributed to the total electricity generated in India as per the pie chart in figure 8.3 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 all the talk that surrounds it, contributes a meagre 2%! And it isn’t expected to contribute more to India’s energy mix even if huge nuclear power plants get built, which in itself is a big if.
The table below summarizes the cost of construction per MW, the pros/cons, and the availability of fuel for the various sources of electricity.
|Method||Cost of Construction (croresperMW)||Cost of Generation (Rs. Per unit)||Pros||Cons|
|Hydro||<0.25||1. Very little running costs 2. Environmentfriendly||1. High setup costs 2. Dependence on water & therefore limited|
|Coal||5-6||1-3||1. Proven technology 2. Low setup & running cost||1. Very harmful to the environment|
|Gas||6-7||1-3||1. Proven technology 2. Low setup &running cost||1. Harmful to the environment although not as much as coal|
|Diesel||Rs.10,000-Rs.20,000 per kW||15+||1. Very low setup cost 2. Is reliable andportable||1. Very harmful to the environment|
|Nuclear||12+||<1||1. High but acceptable setup costs 2. Very low runningcosts||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 a good mix of all of them is required in the total electricity that we generate. However, coal dominates all other energy sources by a fair distance, and that isn’t expected to change in the near future. So the next three articles, a mini-series titled “The Black Truth”, are articles about coal.
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