Chapter – 14 SOURCES OF ENERGY

Sources of Energy: A source of energy provide us sufficient amount of energy which can be used for various purpose.  

Characteristics of Good source of energy or Fuel: A good source of energy should have following characteristics,

1. Eco-friendly: It should not produce smoke and harm full gases or if produced their amount should be minimum so that it does not causes environment pollution.
2. Economical: It cast should be low as much as possible so that needy can afford it.
3. Easy handling: Its transportation and storage should be easy. For example; coal, petrol, diesel, LPG etc. can be stored and transported easily.
4. Clean fuel:  It should produce fewer residues after burning.
5. High calorific value: Its calorific value should be high.
6. Optimum Ignition Temperature: Its ignition temperature should not be too low that fuel can burn self in summer and ignition temperature should not be too high so, that burning this fuel require tremendous amount of work.
7. Safety issue: Fuel should be safe and convenient to use, For example; Nuclear Energy can be used only by highly trained engineers with the help of nuclear power plants. It cannot be used for our household purpose.

Calorific Value: The amount of energy produced by burning 1 gram of fuel is called calorific value. For example; calorific value of LPG is 55kJ/gram and for coal it is 33kJ/gram.

Classification of Source of energy on the basis of their uses:

1. Conventional sources of energy             2. Non- conventional sources of energy

Conventional Sources of Energy	Non-Conventional Sources of Energy
Sources of energy which are used extensively by us from very early period of time. For example; Fossil fuels (coal, oil and natural gas) Hydro-energy Thermal power plant Bio-mass Wind energy	Those Sources of energy which are used as alternate of energy and which use we have learnt only a few decades ago. For example; Solar energy Tidal energy Ocean thermal energy Geothermal energy Nuclear energy

Classification of Sources of energy on the basis of their availability:

1. Renewable sources of energy.                             2. Non-Renewable sources of energy.

	Renewable Sources of Energy	Non-Renewable Sources of Energy
Definition	Sources of energy which are inexhaustible (can not be finished) or which can be renewed in limited time as we use them and can be further used to produce energy again and again.	Sources of energy which are exhaustible (can be finished) and can not be renewed once they have been used or it takes a very long period millions of years to renew.
Example	Solar energy Wind energy Energy from water (hydro-energy) Geothermal energy Ocean thermal energy Tidal energy Biomass energy (wood, cow dung, ethanol)	Fossil fuels like Coal, petroleum and Natural gas. Nuclear energy from nuclear fuels like Uranium
Advantages	Inexhaustible or these sources can be renewed in limited time.These sources are mostly freely available in nature.These sources are Eco-friendly i.e. do not cause environmental pollution.	Economical like diesel petrol and CNG.Easily accessible and easy handling.
Disadvantages	Low energy efficiency and most of them based on environmental condition like sun light, wind velocity, water availability.High capital cast.	Exhausted once they used.Not Eco-friendly causes environmental pollution.Fossil fuel combustion is dangerous to our health.

Fossil Fuels: Fossil fuels are the remains of plants and animals which got buried deep inside the earth, millions of years ago due to some natural processes. Under high pressure, temperature and less availability of oxygen they decay and converted in to coal, petroleum and natural gases.

Advantages of Fossil Fuel:

• Economical, easy handling and optimum ignition temperature so can be used domestic fuel in kitchen and in vehicles.
• Used in thermal power plant so that electricity generation is possible at any location unlike hydro electric power plant, which can be setup in certain areas only.
• They fulfill our most of energy demands.

Disadvantage of Fossil Fuels:

• The fossils are non-renewable sources of energy and used only once.
• Burning of fossil fuels causes air pollution and increases green-house effect.
•  Burning of coal or petroleum produces acidic oxides of Nitrogen and Sulphur which leads to acid rain that affects our water and soil resources. In addition to the problem of air pollution,

Measures to reduce pollution caused by fossil fuels:

• By increasing the efficiency of the combustion process using various techniques.
• By change in released form of gases from more harmful to less using for example using Catalytic Converter more harmful CO can be converted to less harmful CO₂ gas.

Thermal Electric Power Plants: It converts heat energy to electric energy. It receives heat from combustion of coal, petroleum and natural gas so it named ‘thermal’ means heat.

Process:

Heat is produced by burning fuel.

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Steam is produced by utilizing heat energy.

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Steam at high pressure applied to Turbine connected with Dynamo.

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Dynamo converts rotational kinetic energy in to electric energy.

The transmission of electric energy is more efficient than transporting coal or petroleum over long distance.

Hydro Power Plants (Hydroelectricity or Hydel power): It converts kinetic energy or potential energy of water to electric energy.

Process:

Water flowing in a river is stored in a high rise dam and allowed to fall from the top of the dam.

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Water falls on blades of Turbine connected with Dynamo (Electric generator).

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Turbine starts rotating dynamo also (have rotational kinetic energy).

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Dynamo converts rotational kinetic energy in to electric energy.

Advantages of Hydro Power Plant:

• Once setup energy is produced free of cost, requires only maintenance cast not operational cast as in thermal power plant fuel is required always.
• It is eco-friendly and does not produces harmful gases like CO₂, NO_x, SO₂ etc.
• It is a renewable source as water itself is a renewable and inexhaustible resource.

Disadvantages of Hydro Power Plant:

• Huge capital cast i.e. highly expensive to construct.
• Dams cannot be constructed on all river sites water should be available throughout year.
• Large areas of human habitation and agriculture fields get submerged so loss of Flora and fauna.

Improvements in the Technology for using Conventional Sources of Energy:

Solar Energy: The energy obtained from sun is called as solar energy. Solar energy is obtained in the form of heat and light energy.

Solar Constant:  Solar energy received from the Sun per unit time per unit area on an imaginary surface, perpendicular to the Sun’s rays and at Earth’s mean distance from the Sun. For earth solar constant is approximately 1.4 kJ per second per square metre or 1.4 kW/m².

Solar cell/Photovoltaic cell: It is a device which converts solar energy to electric energy. Solar cells are made up of Silicon and Germanium. A Solar cell develops a voltage of 0.5–1 V and can produce about 0.7 W of electricity when exposed to the Sun.

A number of Solar cells are arranged on large flat sheets called Solar Panel.

Uses of Solar cell:

• Used as energy source in satellite, wireless system.
• Used in calculator, toys, street light and traffic signal.
•  Now a days, solar cells are used to setup electric power plant which provide pollution free energy.

Advantages of Solar Cells:

• Its maintenance is easy as it does not contain movable part.
• Eco-friendly does not cause pollution.
• Economical.

Limitations/Disadvantage of Solar Cells:

• Solar cells are less efficient so required in large number to fulfill our energy requirements.
• Can be used primarily in a region where day light time is more.

Solar Cooker: A solar cooker is a device which uses sunlight for heating and cooking.

Working:

Solar light is concentrated to cooking chamber using plane/concave mirror.

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Solar radiation absorb by black surface inside cooking chamber produces heat (converted mostly to Infra-red)

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Glass sheet produces green house effect and trap infra-red radiations inside.

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Temperature inside cooking chamber starts increases slowly.

Working Principle: It works on two principles,

• Black color absorbs heat – Since black color absorbs more amount of heat so solar cooker is painted black inside and cooking utensil also.
• Green house effect – Green house effect is caused by glass sheet covering which trap heat and does not allow heat radiations (Infra-red rays) to reflected back to atmosphere. 

Advantages of Solar Cookers:

• Eco-friendly does not cause pollution.
• Economical.
• Retain all the nutrients in food due to slow cooking.

Disadvantage of Solar Cookers:

• Solar radiations are not uniform over the Earth’s surface and also cannot be used at night or on cloudy days.
• Solar cookers cannot be used to make chapattis or frying as it require a relatively high temperature.

Energy from the Sea:

• Tidal Energy: The rise of ocean water level due to gravitational pull of the moon is known as high tide and its fall as low tide. Due to high and low tide there is enormous movement of water. Tidal energy can be harnessed by constructing a dam near shore.
• Wave Energy: The waves are generated by strong winds blowing across the sea. These sea waves have a lot of kinetic energy associated. This energy can be harnessed using dynamo which convert kinetic energy into electrical energy.
• Ocean Thermal Energy: The energy which is obtained in the form of heat due to temperature difference between upper sea surface and deep sea levels is known as Ocean Thermal Energy.

Source of ocean thermal energy is sun.

This energy can be harnessed by ocean thermal power plant. These plants can operate if the temperature difference between the water at upper sea surface and water at depths up to 2 km is 20 K (20°C) or more. The warm surface-water is used to boil a volatile liquid like ammonia (less boiling plant). The vapours of the liquid are then used to run the turbine of generator. The cold water from the depth of the ocean is pumped up and condense vapour again to liquid.

• Disadvantages: Uniform tidal action is not seen.

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2. Wind Energy: When large masses of air move from one place to another then it is referred to as wind.

During this process, kinetic energy gets associated with it which is referred to as wind energy.

It can be converted into mechanical and electrical energy.

Kinetic energy of wind is used in running of windmills, which are used to lift water, grind grains etc.

Uses of Wind Energy

The important uses of wind energy are :

It is used to drive windmills, water lifting pumps, and flour mills, etc.

It is used to propel sale boats.

It is used to fly engine fewer airplanes or gilders in the air.

It is used to generate electrically used for various purposes like lightning, heating, etc.

Advantages:

Eco-friendly

Renewable.

Disadvantages :

Wind speed does not uniform always.

Needs a large area to erect series of windmills.

Big amount of investment is needed.

The output is less as compared to investment.