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Sources of Electrical Energy

Sources of Electrical Energy-The The major source of Electrical energy in India is fossil fuel and water. An important contribution of electrical energy in India is given below:-
  • Steam power plant
  • Hydropower plant
  •  Nuclear power plant 
  • Diesel power plant
  • Gas power plants
  • Renewable energy sources
During the past few years, the relative contribution of the steam plant has increased. this position is likely to continue due to large pit heads plant being set up.

there are no immediate prospects for large scale utilization of alternate sources of energy like sun, wind, tides, etc.for the generation of electrical energy.  the contribution of diesel and gases is small in spite of the fact that some gas turbine plant is high.

Coal: A solid Fuel and Source of energy

Coal-based Power Plant

In India, Most of the power plant uses coal as a primary source of energy. India has a large storage of good quality coal. I think due to this reason most of the power plant in India is based on coal and uses coal as the primary source of energy.

 If coal is a major source of energy in India then it is much important for us to study the type and nature of different types of coal. Not only in India but also many countries across the world uses coal as the primary source of energy for producing electrical energy.

Classification of Coal

Coal is the most abundant fossil fuel. and it was formed by the decomposition of vegetation which was buried under the earth before millions of years ago. About 20 meters of compact vegetation is required to produce a meter thick seam of coal.
Coal Power Plant
Coal

this compact vegetation in the absence of oxygen and under influence of high pressure and temperature under the earth converted into peat then into brown coal, then into lignite, then into semi-bituminous and finally into anthracite coal. 

Coal consists of mostly carbon as a major content, sulfur, hydrogen, moisture, nitrogen, oxygen, and ash. Coal has the main four categories and is explained below:-

Peat Coal

it is the first stage of conversion of vegetation into coal. It consists of a high percentage of moisture (about 60% to 90 %) and low carbon content.it is not suitable for use in power plants because its calorific value is about 8000KJ/Kg.

Lignite

Lignite has 30% to 50% moisture and 20% to 40 % of carbon. When it is exposed to air its moisture content decrease appreciably.

It can be used in pulverized form for generation of electrical energy.it has a high value of calorific value as compared to peat coal and is about to 20000KJ/Kg

Bituminous Coal

it is the most common variety of coal and is used for almost all-purpose.it has low moisture content and high carbon content as compared above mention two forms of coal and is about 60% to 80% and also it consists very low ash about 5% to 10%.

Semi-bituminous has properties intermediate of bituminous and anthracite and it is widely used in power plants. its calorific value is about 27000KJ/Kg

Anthracite Coal

It is very hard and has the highest percentage of carbon.it is very difficult to pulverize.it is the best form of coal and it has also very high calorific value as compared to above mention all three types of coal and it is about 30000KJ/Kg.

Selection of Coal for Power Plant

The selection of coal for a particular type of power plant depends on different types of factors. Out of which some of them are given below:-

Calorific Value

it represents the amount of energy per kg of coal. High Calorific value of coal is always preferable 

if the calorific value of a particular type of fuel is 2000KJ/Kg.it means that when one kg of this particular type of fuel is combusted, it will produce about 2000000 joules of energy.

Weatherability

it is a measurement of the ability of coal to withstand exposure to the environment without excessive crumbling. Every power plant has considerable storage of coal.

if coal crumbles severely during storage, the small particle will be washed away in a rainstorm causing financial and energy loss and pollution of the surroundings.

Sulfur Content

it is one of the combustible substances in the coal and produces energy on burning. But it has one problem,on burning its primary product is sulfur dioxide and it is a hazard to health.

it is very difficult and expensive  to remove sulfur from coal.it is therefore important that sulfur content of coal is low preferably less than 1.5%

Ash Content

Ash is not pure substance .it does not produce heat energy on combustion and it must be removed from the furnace and disposed of. 

However, a minimum of 4% to 6% ash is required in the coal burnt on hand-fired grates and some smokers to protects the grates from overheating.

Particle Size

The size requirement for different equipment varies widely. Coal burnt on grates must have a certain minimum size to regulate the passage of air through the fuel bed.

for pulverized fuel boiler the coal must be reduced in size to small particles to promote rapid and complete combustion.

  Caking Characteristics

Caking coal produces a fused coal mass as it burns so that much carbon content is not burned.if such coal is used in a power plant the coal bed must be agitated mechanically to break up the fused coal mass. if the coal is to be burned in a stationary bed it should be free burning coal.

Liquid Fuel As Source of Energy


Liquid fuels are the also source of energy.it is obtained from petroleum which contains about 84% to 87% carbon,11% to 16% of hydrogen, and another element like oxygen, nitrogen, sulfur.

liquid fuel has a number of advantages over coal.these advantages are


  • it can be easily handle
  • it is easy to store
  • it can be easily transport
  • it can be easily burn
  • it does not require any type of extra system for handling ash because on burning it does not produce ash.
The crude oil products can be either distillate or residual oil or a mixture of this two.they can be classified as light, medium, and heavy.

Heavy residual oil has high density and viscosity and is sometimes made lighter by blending with distillate oils.

The factors which need consideration in the choice of fuel are cost, calorific value availability, and environmental pollution. Moreover, the choice of fuel also depends on the type of plant.

The diesel engines can operate on many fuels. The cost of fuel accounts for about 60%-70% of the cost of electrical energy in liquid fuel plant therefore the fuel which is cheaper and can meet environmental and operational needs should be selected. 

The liquid fuel which can be used in India for the generation of electrical energy are naptha, high-speed diesel, fuel oil and Low sulfur heavy stock(LSHS)

Naptha

it is a higher-end product of petroleum products and is very commonly used in the petrochemical industry.it is the cleanest of liquid fuels and is a common liquid fuel used in Europe. 

its advantages include low cost, low emissions, good availability, and good turbine efficiency. Naptha required careful handling and storage to ensure that the product does not contaminate with an alkali metal.

Strict guidelines on handling and storage may have adhered because its flash point is generally below the ambient temperature.

High-Speed Diesel

it is also known as gas oil.it has high calorific value but it is slightly expensive.it is cleaner than fuel oil. The government does not allow to use it for the production of electrical energy because it is used by a farmer in the field of agriculture and it is subsidized.

Gaseous Fuel As Source of Energy

Gaseous fuel is either natural or manufactured. The manufactured gaseous fuel is like water gas or producer gas. This manufactured gaseous fuel is costly as compared to natural gas and hence these are not used for the production of electrical energy. 

Natural gas is usually trapped in limestone casings on the top of petroleum reservoirs.it consists of about 80% of methane and remaining other gases and impurity.

its calorific value is about 55000KJ/Kg. Natural gases have given characteristic as compared to solid and liquid fuel:-
  • these are easy to mix with air and easy to burn.
  • these are easy to transport
  • these are clean and ecofriendly
  • it has a low sulfur content
  • it produces low carbon dioxide and other gases as compared to coal and liquid fluid
  • it has high efficiency

Nuclear fuel

The fuel which is used in a nuclear reactor is called nuclear fuel and it is generally uranium, plutonium, and thorium. But in most cases, uranium and enriched uranium dioxide are used as a nuclear fuel in a nuclear reactor.

Natural uranium contains about 0.7% of uranium-235 which is fissile in thermal neutron flux.

Uranium is a hard, dense, and tough material. The calorific value of uranium is very high as compared to the value of coal and other sources of energy.

About 1ton of uranium produces heat equivalent to 10000 tons of coal. The capital cost of a nuclear plant is very high hence the cost of generating electrical energy in a nuclear power plant is high. 

Uranium dioxide is a brittle ceramic produced as a powder.it is more stable than natural uranium and presents fewer problems of oxidation.it does not corrode as easily as natural uranium.

Plutonium-239 is most likely to be used in fast reactors.it is highly toxic. if it enters the body it is retained in bone linings where the alpha particles damage the bone marrow and adjacent blood-forming tissue.

All work on plutonium must be conducted in fully sealed glove boxes.   
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