SOURCES OF ENERGY · 1. FOSSIL FUELS ARE NON-RENEWABLE: The problem with fossil fuels is they will someday run out. It takes time for these energy sources to develop within the crust

SOURCES OF ENERGY A fuel is a substance that is burned to release energy. We use fuels because they have stored energy in the form of chemical energy. To release the energy stored in a fuel, a chemical reaction must take place. The fuel must burn, and to do this, it needs oxygen from the atmosphere. Burning of fuels (combustion): When a fuel is burnt new substance are formed. These usually include carbon dioxide (CO2) and water (H2O). For example in the engine of a car, petrol and air are mixed together. When you turn the key in the ignition, a spark causes and explosion - the petrol burns and the hot gases produced push on a piston to move the car. When a fuel is burned, the chemical energy stored by the fuel is changed to heat energy and often some light energy. chemical energy heat energy + light energy FOSSIL FUELS OBJECTIVES:

1. To define the term fossil fuel 2. To identify how fossil fuels are formed 3. To identify the various types of fossil fuels

FOSSIL FUELS:

All living things contain carbon. When they die and decompose, in conditions where oxygen is limited, over millions of years, fossils are formed. Fossils which can be burnt to produce energy are called fossil fuels.

FORMATION OF FOSSIL FUELS:

Millions of years ago, plants and animals died because of massive natural disasters such as earthquakes and volcanic eruptions. Their remains got buried under soil sediments for millions of years.

Since these remains were so far underground, they were exposed to anaerobic bacteria (bacteria which decompose things without oxygen). Under the earth, the remains were also subjected to high pressures, high temperatures and limited oxygen.

Due to the above conditions, the remains decomposed into materials such as coal, petroleum and natural gas. All three of these materials are known as fossil fuels.

THE VARIOUS TYPES OF FOSSIL FUELS:

There are three main types of fossil fuels: natural gas, coal and petroleum

Fossil fuels are non-renewable. This means that once used once they cannot be used again. It takes millions of years for them to be formed.

The source of the energy of fossil fuels is Sun. The energy from the Sun is trapped and stored as chemical energy in plants (and then transferred to animals).This energy is then released as heat and light energy by the fossil fuels on burning.

Petroleum or crude oil is a complex mixture of hydrocarbons. A hydrocarbon is a compound which contains hydrogen and carbon. Petroleum is separated out into fractions by fractional distillation. Each fraction has different uses. For example, the heavier fractions such as bitumen (asphalt) are used for road paving. The lighter fractions such as refinery gas are used in homes as cooking gas.

Diagram showing fractional distillation of crude oil

The following experiment is designed to show that upon combustion (burning), energy can be evolved from petroleum.

The principle of this experiment is that kerosene (commonly known as pitch oil) is a fraction of petroleum. When kerosene is burnt, it produces heat. This indicates that energy (in the form of heat) is released upon burning.

AIM: To demonstrate that energy is evolved from petroleum fractions (such as kerosene) upon burning

APPARATUS:

• 100 ml beaker

• 80 ml distilled water

• Thermometer

• Test Tube

• 10 ml kerosene

• Bunsen Burner

PROCEDURE:

1. The 100 ml beaker was filled with 80 ml of water and placed on the unlit Bunsen Burner

2. The temperature of the water was taken and recorded

3. The test tube was filled with 10 ml of kerosene and placed inside of the 100 ml beaker

4. The Bunsen Burner was lit and the apparatus left to stand for ten minutes

5. After ten minutes, the temperature of the water in the 100 ml beaker was again taken.

OBSERVATIONS:

Final temperature of water (after 10 minutes) = 40 ᴏ C

Initial temperature of water (before heating) = 30 ᴏ C

Change in temperature = 40 ᴏ C - 30 ᴏ C = 10 ᴏ C

CONCLUSION: Since there was an increase in temperature of the water when the kerosene was heated, this indicated that heat energy was being released. It can be concluded that there is potential energy in petroleum and its fractions. When burnt, this energy is released.

COMBUSTION OF FOSSIL FUELS Combustion is the process by which organic compounds burn in oxygen to produce carbon dioxide, water and energy: Fuel + Oxygen + burning Carbon Dioxide + Water + Energy LUMINOUS AND NON-LUMINOUS FLAMES Non-luminous flames

• Have a low ratio of fuel to oxygen

• Are clean, blue and non-smoky

• Have a very high heat/light ratio

Luminous flames

• Have a high ratio of fuel to oxygen

• Are yellow and smoky

• Have a low heat/light ratio

PROBLEMS WITH FOSSIL FUELS

1. FOSSIL FUELS ARE NON-RENEWABLE:

The problem with fossil fuels is they will someday run out. It takes time for these energy

sources to develop within the crust of the earth. At the current rate of consumption, there

is no way that these fuels can develop naturally and not be used up. Fossil fuels are thus

said to be non-renewable. Currently there are ways being developed to sustain these

fuels.

More efficient uses are these energies are being produced. Cars with better gas mileage

are being manufactured. Hybrid cars which use electricity as well as gas are just one of

the many products which have been developed to sustain the use of fossil fuels. Still these

fuels are being depleted.

2. FOSSIL FUELS GIVE RISE TO POLLUTION:

Another problem with the use of fossils fuels is no matter how safely and efficiently these

fuels are being used, they still have an impact on the environment. The combustion of

these fuels contributes pollutants to the atmosphere such as carbon dioxide CO2, carbon

monoxide CO and sulphur dioxide SO2.

• Carbon dioxide builds up in the atmosphere trapping heat energy. This absorption

of energy causes the CO2 molecules to heat up and vibrate. The heat produced is

reflected back to the earth’s surface. This causes the earth to heat up. This entire

process is known as the greenhouse effect. It follows that the greenhouse effect

causes atmospheric (global) warming, which results in ice caps melting and

extensive flooding.

• Carbon monoxide combines with haemoglobin in the blood. It forms

carboxyhaemoglobin which prevents blood carrying oxygen, resulting in

headaches, unconsciousness and death.

• Sulphur dioxide combines with water vapor and smoke to form smog. Smog

causes respiratory diseases and even death.

• Sulphur dioxide also dissolves in rainwater to form an acidic solution (weak

sulphuric acid) which is also known as acid rain. Acid rain is harmful to plants

and animals and causes corrosion of structures and buildings.

The greenhouse effect is explained in the following diagram:

Alternatives are being developed. Fossils fuels cannot last forever at the current rate of

consumption. Alternatives are being developed to sustain the lifestyles that we have

become accustomed too. In time, fossil fuels will be a thing of the past.

Alternative sources of energy are as follows:

1. Solar Energy: All of our energy comes indirectly from the sun. Through the use of technology, the energy from the sun can be trapped and used to provide energy. This is done mainly by:

(i) Solar water heaters (ii) Solar panels that trap and convert solar energy into electricity (iii) Solar Crop Dryers (iv) Solar Stills that distil sea water Advantages of Solar Energy:

• It is readily available in large quantities (especially in Caribbean countries)

• It is a renewable energy source Disadvantages of Solar Energy:

• Unreliability of the sun: It is subject to seasonal changes (impossible to obtain at night and during winter)

2. Biogas: When organic matter is decomposed in the absence of oxygen (anaerobically), biogas is produced. Animal waste is placed in a digester and left to decompose. The gas produced is 60-70% methane, and small amounts of water vapor, nitrogen, hydrogen sulphide and carbon dioxide. Biogas can be used for cooking, lighting, refrigeration and heating.

Advantages of Biogas:

• Biogas is inexpensive • Biogas is a method of waste disposal

Disadvantages of Biogas:

• Cannot be used in regions where pastoral farming is not practiced

3. Wind: Wind is harnessed by windmills. The windmills turn turbines which is necessary to produce electricity. Windmills can also be used to pump water and run air circulation units.

Advantages of Wind Energy:

• It is a renewable energy source • It is readily available

Disadvantages of Wind Energy:

• Wind speeds are variable and unreliable • Creates a lot of noise pollution

4. Wave: Waves are created from the transfer of wind energy which blow over them. Waves transfer energy to the shore where it is utilized by a shoreline power station in order to produce electricity,

Advantages of Wave Energy: • It is a renewable energy source

Disadvantages of Wave Energy:

• This is a relatively new alternative energy source and as such has inherent problems which are yet to be resolved.

5. Bio-fuels: Bio-fuels are any kind of fuels made from plants or animals. A common example of this is ethanol which is cheaply produced by the fermentation of sugar. It is used to produce gasohol which contains gasoline 80% and alcohol 20%. This can be used as a fuel in cars.

Advantages of bio-fuels:

• Cheaper than gasoline • Less pollution is produced

Disadvantages of bio-fuels:

• Limits the amount of organic material which can serve other uses such as fertilizers.

6. Geothermal:

This is energy derived from the internal heat of the earth. Heated rock and molten magma, deep under the earth’s surface contain lots of energy. This energy can be harnessed to provide heating and to produce electricity. Cold water is pumped downwards into the earth. It is heated naturally by the heated rock and magma, and returns to the surface of the earth as steam, which can generate electricity.

Advantages of Geothermal Energy: • It is a renewable energy source Disadvantages of Geothermal Energy: • Carbon dioxide and hydrogen sulphide emissions may be high and this

contributes to pollution • The water supply may become saline • Earth movements can damage power stations

7. Hydroelectric: Waterfalls are cascades of water at high pressure. Power plants utilize the force of a waterfall to turn turbines to produce electricity.

Advantages of Hydroelectric Energy: • It is a reliable, renewable, efficient energy source: In countries where

waterfalls are not natural, dams can be built to increase the pressure at which water falls.

Disadvantages of Hydroelectric Energy: • Cost of setting up power plants and for transport of electricity produced is

very high. However, once a scheme is operating, producing electricity is cheaper than that produced by fossil fuels.

• Dams can be a flood risk if they collapse or overflow, and are believed to be linked to earthquake activity

8.)Biodiesel: Biodiesel is a natural and renewable domestic fuel alternative for diesel engines made from vegetable oils, mostly soy and corn. It contains no petroleum, is nontoxic and biodegradable. Biodiesel is made using an alcohol like methanol and a chemical process that separates glycerine and methyl esters (biodiesel) from fats or vegetable oils.

Advantages: Biodiesel burns clean, which results in a significant reduction of the types of pollutants that contribute to smog and global warming and emits up to 85% fewer cancer-causing agents.

Disadvantages: Growing crops requires time and significant investment, and the fuel must be made and shipped to a local station. For these reasons biodiesel is more expensive than petroleum, gallon for gallon.

No one alternative source will solve the problems posed by global warming. Wind energy does have potential, biofuels are possibilities, but all these have associated problems as well. Coupled with more investment and better technology, the solution should come from a combination of all these sources.

HEAT TRANSFER

Heat energy can be transferred from a place where it is very hot to a place where it is not so hot. There are three methods of heat transfer: conduction, convection and radiation.

Conduction:

Conduction is the transfer of heat energy through a material without movement of the material itself. This is the usual method of heat transfer in solids. Some materials are good conductors, for example metals are good conductors of heat. Some materials are poor conductors (insulators), for example air, glass and wood.

Convection:

Convection is the transfer of heat energy by the circulation of fluids from one place to another due to differences in temperature. If you drop a large crystal of potassium permanganate into a beaker of water and then heat the beaker gently, you will observe an upward current of coloured water which spreads out at the surface and then moves down the sides of the beaker. This movement is called convection currents.

Convection currents are responsible for land and sea breezes. During the day the land is hotter than the sea. Hot air from the land rises and cold air from the sea moves in to take its place. During the night the sea is hotter than the land. Hot air rising from the sea is replaced by cold air from the land.

Radiation:

Radiation is the transfer of heat energy by means of electromagnetic waves. Unlike convection and conduction, radiation takes place without a material medium. Heat travels from the Sun to the Earth by radiation.

LAND AND SEA BREEZES

Land and sea breezes are actually convection currents (remember convection from temperature control).

During the day, the land heats up more rapidly than the sea, hence the heated air rises from the land and an area of relatively lower pressure is formed, Sea breeze begins to blow from the sea towards the land to replace the rising air.

However, as the land loses heat more quickly and becomes cooler than the sea at night, the opposite occurs. Land Breeze blows from the cooler land (area of high pressure) towards the warmer sea (area of lower pressure).