[Physics Class Notes] on Conventional Sources of Energy – Fossil Fuels Pdf for Exam

For many years, burning fossil fuels has generated most of the energy required to propel our cars, power our businesses, and keep the lights on in our homes. 

Even at present, oil, coal, and gas provide for about 80 percent of our energy needs.

How fossil fuels are formed?

Coal, crude oil, and natural gas are regarded as fossil fuels because they were formed from the fossilized, buried remains of plants and animals that lived millions of years ago. They were decomposed by microorganisms that led to the formation of fossil fuels. Fossil fuels have a high carbon content.

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Fossil Fuels Examples

1. Oil

Crude oil or petroleum is a Latin word meaning, ‘rock oil.’ It is a liquid fossil fuel that is formed of hydrocarbon compounds that can be found in underground reservoirs, in the cracks, crevices, sedimentary rocks, or in the tar sands near the earth’s surface.

Oil is obtained by drilling, on land or at sea, or by strip mining in the case of tar sands oil and oil shale. 

Once the oil is extracted, it is channelized to refineries through supertanker, train, truck, or pipeline for a metamorphosis of it into usable fuels such as gasoline, propane, kerosene, and jet fuel, and in products such as plastics and paint.

Fact: Petroleum products supply about 37 percent of the energy needs of the U.S.

2. Coal

Coal is a hard carbon-heavy rock that can be burned as a solid fossil fuel. It is mostly carbon; however, it also contains hydrogen, sulfur, oxygen, and nitrogen.

It comes in four main varieties differentiated largely by carbon content, namely,

Coal is obtained by two methods:

• Underground Mining: We use heavy machinery to cut coal from deep underground deposits.

• Surface Mining: It is strip mining, it removes entire layers of soil and rock to access coal deposits buried deep.

Fact: Strip mining accounts for about two-thirds of coal sourced in the United States.

3. Natural Gas

Natural gas is also called fossil gas. It is a naturally occurring hydrocarbon gas mixture that is mainly composed of methane. It also includes varying higher amounts of alkanes, and sometimes it contains a percentage of nitrogen, carbon dioxide, hydrogen sulfide, or helium.

It can be either conventional or non-conventional based upon the place where they are found underground.

• Conventional Natural Gas: This gas is located in porous rock beds that can be accessed via standard drilling.

• Unconventional Natural Gas: It isn’t easy to extract this gas through a regular drilling process. A special technique named fracking is used for its extraction.

Effects of Fossil Fuels

The harmful effects of fossil fuels are outlined below:

1. Land Degradation

During the process of extraction of fossil fuels, processes like unearthing, processing moving underground oil, gas, and coal deposits takes an enormous toll on our landscapes and ecosystems.

The fossil fuels dispose the waste disposal into the wells, on the land, because of this, the wildlife habitat that relies on the land for breeding gets destroyed.

2. Air Pollution

Burning coal releases unsafe compounds like sulfur oxide. During the combustion of car engines and power plants, gases are released into the atmosphere because of which the depletion of the ozone layer occurs, and UV-rays reach directly to the earth possessing damage to the living beings.

3. Water Pollution

Industries disposing waste into the water have high amounts of mercury, which pollutes the drinking water and jeopardizes the freshwater ecosystem.

4. Global Warming

Burning of fossil fuels emits a lot of greenhouse gases like carbon dioxide into the atmosphere, causing an increase in the temperature of the atmosphere. Global warming leads to the melting of glaciers causing rising sea levels.

Thermal Power Plant

A fossil fuel power plant is a thermal power plant that burns fossil fuels such as coal, petroleum, or natural gas to produce electricity.

They are designed on a large scale for continuous operations, and in many countries, the plant provides most of the electrical energy.

Working of Thermal Power Plant

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Thermal power plants work on the principle of the Rankine cycle.

From, Process 1-3: In a boiler, the coal is burned to produce the heat.

Process 3-4: A high-pressure and high-temperature steam is passed through the pipe to the inlet of the turbine. 

This steam hits the turbine blades and makes the turbine rotate. Here, the conversion of heat energy into mechanical energy takes place.

Process 4-5: The steam escapes from the outlet of the turbine to enter the condenser, which is just below the turbine. 

The steam in the condenser converts into the water with the help of the coolest indirect heat exchange. A major amount of energy loss occurs here.

Process 5-1: In the condenser, the bottom water is collected. This water is again pumped in a boiler with the help of a heavy pump called a boiler feed pump.

Apart from the Diagram

There are two high-pressure turbines joined one after the other followed by a low-pressure turbine that starts rotating, and sets the generator into motion. The high-pressure turbine is about 170 bar and temperature of about 353°C, while a low-pressure turbine with ~ 0.1 bar pressure and temperature as low as 40°C. This converts mechanical energy into electrical energy.