Physics Topics can help us understand the behavior of the natural world around us.
What is a thermal power plant and how does it works
An installation where electricity (or electrical power) is generated is called a power plant. A power plant is also called a power house or power station. A power plant in which the heat required to make steam to drive turbines (to make electricity) is obtained by burning fuels (coal, oil or gas) is called thermal power plant. We will now decribe how fossil fuels are used to produce electricity.
Coal (fuel oil or natural gas) is burned in a furnace F to produce heat (see Figure). This heat boils the water in a boiler B to form steam. The steam formed from the boiling water builds up a pressure. The hot steam at high pressure is introduced into a turbine chamber C having a steam turbine T. The steam passes over the blades of the turbine as a high pressure jet making the turbine rotate (see Figure).
The shaft S of turbine is connected to a generator G. When the turbine rotates, its shaft also rotates and drives the generator. The generator produces electricity. The spent steam coming out of turbine chamber is cooled.
On cooling, steam condenses to form water. This water is again sent to the boiler to form fresh steam. This process is repeated again and again.
Since it is easier to transmit electricity over long distances than to carry coal (oil or gas) over the same distance, therefore, many thermal power plants are established near coal fields (or oil fields). We produce a major part of our electricity by burning fossil fuels. Due to this, large amounts of fossil fuels (coal, oil and gas) are being burnt everyday at thermal power plants to generate electricity.
Because our supplies of coal, oil and gas are running out at a rapid rate, and because of the pollution caused by burning fossil fuels, other ways of generating electricity must be found. Please note that electricity is not a fuel. It is a form of energy. At thermal power plants, it is the chemical energy of fossil fuels (coal, oil and gas) which is transformed into electrical energy.
Pollution Caused by Fossil Fuels
The main disadvantage of using fossil fuels is that the burning (or combustion) of fossils fuels causes a lot of pollution in the environment. This is explained below.
1. The burning of fossil fuels produces acidic gases such as sulphur dioxide and nitrogen oxides. These acidic gases cause acid rain. The acid rain damages trees and plants .(crops, etc.), reduces fertility of soil by making it acidic, and poses a danger to aquatic life (like fish) by making the water of lakes and rivers acidic. Acid rain damages buildings by corroding them slowly. The monuments made of marble stone and statues are also damaged by acid rain. The burning of fossil fuels also puts a poisonous gas, carbon monoxide, into air.
2. The burning of fossil fuels produces large amount of carbon dioxide which goes into air. Though carbon dioxide gas is not harmful immediately, it damages the environment in the long run. The presence of increasing amounts of carbon dioxide gas in the atmosphere is causing increased greenhouse effect leading to excessive heating of the earth. This is harmful for all the life on earth.
3. The burning of fossil fuels (especially coal) produces smoke which pollutes the air.
4. The burning of coal leaves behind a lot of ash. It also puts tiny particles of ash (called fly-ash) into the air causing air pollution.
Controlling Pollution Caused by Fossil Fuels
The pollution caused by burning fossil fuels can be controlled (or reduced) to some extent by increasing the efficiency of the combustion process, and by using various techniques to reduce the escape of harmful gases and ash into the surrounding air. This will become clear from the following discussion.
1. The pollution of air caused by burning petroleum fuels (like petrol and diesel) in vehicles can be controlled by fitting the vehicles with catalytic converters (see Figure). The catalytic converter is a device which changes the harmful gases coming from the engine of a car into harmless gases before releasing them into air.
For example, the catalytic converter brings about the complete combustion of the poisonous gas carbon monoxide to form carbon dioxide which is not poisonous at all. It also changes harmful nitrogen oxides into harmless nitrogen gas. The catalytic converter is fitted in the exhaust system of a vehicle (like a car).
2. The pollution of air caused by burning coal in thermal power plants and factories can be controlled by washing down the smoke and acidic gases by water in a scrubber. Scrubbers are tanks where the smoke and waste gases produced by thermal power plants and factories, etc., are sprayed by jets of water before they reach the chimney. Water washes away soot (carbon) present in smoke and dissolves most of the harmful acidic gases like sulphur dioxide and nitrogen oxides.
3. The pollution of air caused by burning coal in thermal power plants and factories can also be controlled by installing electrostatic precipitators in their chimneys. When an electrostatic precipitator is installed in the chimney, then the unburnt carbon particles and fly-ash particles present in smoke keep on depositing on the inner walls of the chimney and do not go into air. The ‘deposit’ of carbon and fly-ash particles can be removed by sweeping the chimney from time to time.
Effect of Industrialisation
All the factories and companies which are engaged in the process of manufacturing goods from raw materials, taken together, are called an industry. The process of developing industries in a country on a large scale is called industrialisation. Industrialisation has led to a better quality of life of the people all over the world.
But the setting up of industries and running them needs energy. So, the increasing industrialisation has caused the demand for energy to grow at a tremendous rate. At present, the growing demand for energy is largely met through the use of fossil fuels : coal, petroleum and natural gas.
The fossil fuels have been used at such a fast pace in the past that only limited reserves of these fuels are now left in the earth. Even today, we are mainly dependent on the fossil fuels for our energy needs. If we continue to consume fossil fuels at such a rapid rate, they will soon get exhausted.
And since fossil fuels, which we are using today, were formed very, very slowly over the past millions of years, so once exhausted they will not be available to us in the near future. This will create an energy crisis. In order to avoid running out of fossil fuels and face an energy crisis, we should explore alternative sources of energy which do not depend on the fuels dug out from the earth.
This will help us conserve fossil fuels for a much longer time to come. Thus, we are looking at the alternative sources of energy because of the following reasons :
- The fossil fuel reserves in the earth are limited which may get exhausted soon if continued to be used at the current rate,
- The use of alternative sources of energy will reduce pressure on fossil fuels making them last for a much longer time, and
- By using alternative sources of energy, the pollution being caused by the burning of fossil fuels can be avoided.