Lesson 14 - Sources of Energy-Class 10 Science Notes

 Sources of Energy

Energy:- In physics, energy is the capacity for doing work.

Or

Energy is defined as the ability to do work.

 

Types of Energy:-  Energy comes in various forms-

1. Kinetic energy                             

2. Potential energy

3. Thermal energy

4. Electrical energy

5. Chemical energy  

6. Light energy

7. Sound energy

8. Wave energy

9. Gravitational energy

10. Wind energy

1. Kinetic energy:- Kinetic energy is the energy of motion of a body.

Example- Child swinging on a swing.

2. Potential energy:- Potential energy is the energy of object’s position.

Example- Energy of ball at highest point while throwing.

3. Thermal energy:- Thermal energy or heat energy reflects the temperature difference between to systems.

Example:- A cup of tea has thermal energy.

4. Electrical energy:- Electrical energy is the movement of electrons.

Example- Electricity used in homes.

5. Chemical energy:- Chemical energy is the energy stored in the bonds of chemical compounds.

Example- Energy in fuels like wood, coal and petroleum.

6. Light energy:- Light energy is the form of electromagnetic radiation.

Example- Energy which enables us to visible.

7. Sound energy:- Sound energy is the movement of energy through substances.

Example- Energy which enables our ears to hear.

8. Wave energy:- Wave energy is a form of energy that can be harnessed from the motion of waves.

9. Gravitational energy:- Gravitational energy is a form of potential energy. It is an energy associated with gravity.

10. Wind energy:- Wind energy is the use of wind to provide mechanical energy to turn into electrical energy.

11. Nuclear energy:- Nuclear energy is the energy that is trapped inside the nucleus of an atom. It can be produced by fission (Splitting of atoms) or fusion (Combining of atoms) process.

 Conservation of Energy:- Energy can neither be created nor be destroyed, it can only be transformed into one form to another from.

Example- 1. If we drop a plate from a height, the potential energy of the plate is converted mostly to sound energy when it hits the ground.

2.If we light a candle, the process is highly exothermic so that the chemical energy in the wax is converted to heat energy and light energy on burning.

Need of energy:- Energy is needed for

i. Making food

ii. Lighting

iii. Transport

iv. Running machines

v.  Industrial activities and

vi. Agricultural work

Fuels:- The materials which are burnt to produce heat energy are known as fuels.

            Example- wood, coal, LPG, kerosene etc.

Good Fuels:- Fuels which would do a large amount of work per unit volume or mass, be easily accessible and be easy to store and transport are called good fuels.

Properties of good fuels:- Properties of good fuels are-

i. High calorific value i.e. give more heat per unit mass

ii. Burn without giving out any smoke or harmful gasses.

iii. Leaves less residue after burning.

iv. Proper ignition temperature

v. Cheap and easily available

vi. Easy to handle, safe to transport

vii. Convenient to store.

viii. Burn smoothly

Sources of Energy:- Anything that provides us energy is called a source of energy. 

Example- Solar energy, Wind energy, Biofuels, and Geothermal energy etc.

Types of sources of energy:- Sources of energy can be classified as-

1. On the basis of Availability

i. Renewable sources of energy

ii. Non- renewable sources of energy

i. Renewable sources of energy:- These are resources that can be used again and again. or    we can say that these resources will not finish easily and will last for a long time.

These are available in an unlimited amount in nature and develop within a relatively short period of time.

Example- Examples of renewable sources are-

•  Solar energy
• Wind energy
• Water energy (hydro energy)
• Geothermal energy
• Ocean energy
• Biomass energy (firewood, animal dunk, degradable waste.

Advantage of Renewable sources of Energy:-

• These sources will last as long as the earth receives light from the sun
•  These sources are freely available in nature
• These sources do not cause any pollution

ii. Non- Renewable sources of energy:- these sources of energy are those which are exhaustible and cannot be replaced once they have been used. These sources have been accumulated in nature over a very long period of time.

Example- Examples of non-renewable sources are-

• Coal
• Oil
• Natural gas

All these are called fossil fuels.

Disadvantage of Non-renewable sources of Energy:-

• Due to their extensive use, these sources are fast depleting
• It is difficult to discover and exploit new deposits of these sources.
• These sources are a major cause of environmental pollution

Difference between Renewable and Non-renewable sources of energy:-

Renewable source of energy	Non-renewable source of energy
1.These sources are available in unlimited amount .	1.These sources are not available in unlimited amount.
2.These sources can be used again and again for long years.	2.These sources cannot be used again and again.
3.These are not exhaustible.	3.These are exhaustible.
4.Wind, water, biomass, solar energy etc.	4.Coal, petroleum, natural gas etc.

2. On the basis of Use

i. Conventional sources of energy

ii. Non-conventional sources of energy

i. Conventional sources of energy:- Conventional sources of energy are those which are used extensively and meet a marked portion of our energy requirement.

Example-

•  Fossil fuels (coal, oil and natural gas)
• Hydro energy (energy of water flowing in rivers)
• Biomass energy and wind energy also called conventional source of energy as these are being used since ancient times.

ii. Non-conventional/Alternative sources of energy:- Non-conventional sources of energy are those which are not used extensively as the conventional ones and meet our energy requirement only on a limited scale.

Example-

• Solar energy
• Ocean energy (tidal energy, wave energy, ocean thermal energy(OTE))
• Geothermal energy
• Nuclear energy

These sources of energy which have been tapped with the aid of advances in technology to meet our growing energy needs are also called alternative sources of energy.

Fossil fuel:- Those fuels which form by fossils of living organisms by the biochemical processes over millions of years. These fuels are called fossil fuels.

These fossils fuels are non-renewable sources of energy and cause environmental problems due to pollution.

Example- coal, petroleum and natural gas. 

Formation of fossil fuels:- They are formed when dead plants and animals get buried under the earth over millions of years and due to high pressure and temperature, they get transformed into fossil fuels. They are non-renewable resources, so their wise use is recommended.

Coal:- It is a sedimentary rock that burns. It mainly contains carbon, hydrogen and oxygen. It also has some quantity of nitrogen and Sulphur.

Different types of coal:-

i.                    Peat  

      

ii.                 Lignite

iii.               Bituminous

iv. Anthracite

Dependence on coal as a source of energy:-

i. The usage/exploitation of coal has been made the industrial revolution possib

ii. We are even today depended on fossil fuels like coal and petroleum for the supply of the growing demand of energy.

iii. Even today most of our energy requirements (about 70%) are used by fossil fuels mainly coals.

Natural gas:- 

• It has mixture of alkanes i.e. 80% methane, 7% ethane, 6% propane and 4% butane.
• It occurs deep in the earth’s crust with petroleum deposits.
• Propane and butane are separated from natural gas and are liquefied under pressure to form LPG (Liquefied Petroleum Gas) and used as domestic and industrial fuel.
• CNG (Compressed natural Gas) having main constituent methane is also used as a fuel in vehicles and in industries.

   

Petroleum:- The name of petroleum means rock oil (Petra means rock and Oleum means oil). It is called petroleum because it is found in the crust of the earth, trapped in rocks. A range of fossil hydrocarbons that are found as gasses, liquids and solids beneath the earth’s surface. The two common forms of petroleum are crude oil and natural gas.

Crude oil:- It is a complex mixture of alkane hydrocarbons with water and earth particles. The final stage of refining involves the removal of impurities such as Sulphur compounds.

            When a fuel contain Sulphur is burnt, the Sulphur in it turns into Sulphur dioxide which is an acidic gas. So it is to be purified or refined before it can be used for specific purpose.

The process of separating crude petroleum oil into more useful fractions is called refining. The refining of petrol is done by the process of fractional distillation.

Advantage of fossil fuels:-

• As domestic fuels- coals, kerosene and natural gases.
• Uses in vehicles – petrol, diesel and CNG
• Uses of coals and other fossil fuels in the thermal power plant

Disadvantage of fossil fuels:-

• The fossils are non-renewable sources of energy and once used cannot be renewed.
• Burning of fossil fuels causes air pollution.
• The fossil fuels reserves in the earth are limited and may get exhausted soon.
• They produce a lot of carbon dioxide that causes the greenhouse effect.
• They produce a lot of smoke
• They releases oxides of carbon, nitrogen and Sulphur on burning that causes acid rain.

Controlling pollution caused by fossil fuels:-

1. By increasing the efficiency of the combustion process.
2. Using various techniques to reduce the escape of harmful gases and ashes into the surroundings.
3. We should conserve the fossil fuels.

Reasons for conserving fossil fuels:-

i. Fossil fuels are non-renewable source of energy.

ii. These are in limited quantity in nature.

iii. These form in over millions years.

The principle of Turbines:- Turbines work by mechanical energy, there have to provide a movement to spin its rotor-blade. This movement is acquired by moving materials like water, stem or by the air. It provides energy to rotor. This rotor turns the shaft of the dynamo in order to transforming this provided mechanical energy into electrical energy. This the principle of turbines.

The process of producing electricity:- In the process of producing electricity, there is used the various sources of energy to turn the turbines. These are the following sources of energy.

i. By falling water from high.

ii. Producing steam by heating water.

iii. By high speed wind.

 

This process is as follows-

1. Turning the turbine by using energy sources

2. Mechanical energy given by turbine to turn the shaft of dynamo

3. Producing electrical energy by the Dynamo

Thermal Power Plants:-  It generates electricity from heat produced by combustion of fossil fuels.

Example:- Coal and Petroleum.

        Large amount of fossil fuels are burnt every day in power stations to heat up water to produce steam from water. This steam has kinetic energy and allowed to rotate blades of turbines which is further attached to a generator. When coil of generator rotates, electric energy is produced.

        

Hydro power Plant:- It is the arrangement in which the kinetic energy of flowing water is transformed into electric energy. The electric energy thus generated is called hydroelectricity.

            In Hydroelectric Power Plant, water is stored at a height in reservoirs provided with gates. These gates are opened and water is allowed to flow where its potential gets converted into kinetic energy. This energy rotated the blades of turbines which is further coupled to a generator. When the coil of the armature of the generator rotates, electric energy is produced.

Advantage of Hydro power Plant:-

1. No environment pollution.
2. Flowing water is a renewable source of energy.
3. Construction of dams prevents flooding of rivers, provide water for irrigation.

Disadvantage of Hydro Power Plant:-

1. Large areas of agriculture land, a vast variety of flora and fauna, human settlements get submerged in the water of reservoir formed by the rain.
2. Large ecosystems are destroyed.
3. Vegetation that submerged under water rots under anaerobic conditions and produces large amount of methane which is a greenhouse gas.
4. Creates the problems of satisfactory rehabilitation of displaced people.

Wind Energy:- When large msasses 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 to running of windmills, which are used to lift water, grind grains etc.

Structure of Wind mill:- A windmill essentially consists of a structure similar to a large electric fan that is erected at some height on a rigid support. In this blades of wind mill are connected to a electric generator. When air rotates blades, the armature of generator moves and generates electricity.

Wind Energy Farm:- A number of windmills are erected over a large area, which is known as wind energy farm.

Commercial use of Wind mill:- The energy output of each windmill in a farm is coupled together to get electricity on a commercial scale. By resulting obtained net energy is the sum of electric energy produced by the all wind mill.

Uses of Wind Energy:-

1. It is used to drive windmills, water lifting pumps, and flour mills, etc.
2. It is used to propel sale boats.
3. It is used to fly engine fewer airplanes or gliders in the air.
4. It is used to generate electrically used for various purposes like lighting, heating, etc.

Advantages of Wind Energy:-

1. Wind energy is an environment-friendly and efficient source of renewable energy.
2. It requires no recurring expense for the production of electricity.

Limitation of Wind Energy:-

1. Wind energy farms can be established only at those places where wind blows for the greater part of a year.
2. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine.
3. There should be some back-up facilities like storage cells.
4. Establishment of wind energy farms requires large area of land.
5. For 1 MW generator, the farm needs about 2 hectares of land.
6. The initial cost of establishment of the farm is quite high.

Bio- Mass:- Bio-mass is defined as living matter or its residue and is a renewable sources of energy.

The bio-mass includes-

• All the new plant growth
• Agriculture and forest residues (like: Bio-gasses, dark, sea dust, wood saving, roots, animals dropping, etc.
• Carbonaceous wastes (like: sewage, garbage, night-soil, etc)
• Biodegradable organic effluent from industries.
• It is the source of the conventionally used fuels that are used in our country.

Example:- Cow dung, cakes, fire-wood, coal, charcoal, etc.

Bio-gas:- It is a mixture of methane, carbon dioxide, hydrogen and traces of hydrogen sulphide. It is produced due to anaerobic fermentation of biomass.

Formation of Bio-gas:-  Cattle dung and slury is mixed in equal propotions and is fed into the digester tank where it is left for few days. In the digester, fermentation takes place that is bacteria or micro-organisms produce enzymes, that in anaerobic condition start converting it into simple substance.

            Along with simple substance, biogas is produced which starts collecting in the dome. As the volume of gas collected increases, it pushes the used slurry into overflow tank and with time. It is filled again with slurry and the process goes on occurring. We can take the gas out from the pipe and use it for various purposes.

Advantage of Biogas as fuel:-

1. The spent slurry being rich in nitrogen and phosphorus is used as manure.
2. It is used for domestic cooking.
3. It is eco-friendly.
4. It leaves no residue.
5. It is also used for illumination purpose.
6. It is clean fuel that burns without smoke and leaves no ash.
7. The main constituent of bio-gas i.e. ethane has a higher calorific value (55kj/g) that of petrol (50 KJ/g)
8. By using bio-gas, firewood is saved and deforestation is reduced.

Composition of Bio-gas:- Bio-gas is mainly composed of methane (up to 75%), carbon dioxide (25%) and traces of other gases such as nitrogen and hydrogen. Whereas methane is a high calorific fuel, carbon dioxide is an inert gas.

 

Non-conventional/Alternative sources of Energy

Causes to look at non-conventional sources of energy:

i.                    The demand of energy increasing day by day, but these all demands cannot be completed by conventional sources of energy.

ii.                 Conventional sources are limited in nature.

iii.               Conventional sources like fossil fuels are very low that can be finished in future.

iv.               The most of the conventional sources of energy is non-renewable.

Solar Energy:- The energy obtained from sun is known as solar energy. It is a renewable source. This energy helps in keeping the temperature of earth hotter, causes air currents in the atmosphere and causes water cycle and also helps in photosynthesis.

Solar constant:- It is the total energy that falls on 1 meter square area in 1 second.

                        Solar constant=1.4 KJ/s/m² or 1.4 KW/m²

Limitations of Solar Energy:-

i.                    It falls in diffused form.

ii.                 It is not available all the time.

iii.               It is not available at a constant rate.

iv.               It is not available at night.

v.                 It is not available at all places.

Solar energy devices:- These are the devices that work on solar energy-

i.                    Solar cooker

ii.                 Solar water heater

iii.               Solar cells

i. Solar cooker:- Solar cooker is a device which is used to cook food by using solar energy. It is of two types- Box type and Concave reflector type.

Principle of Solar cooker:- There are two principles on which solar cooker works-

a.      Black color absorbs more heat than other.

b.     Use of glass plate which produces green-house effect inside the cooker.

Structure and function of solar cooker:- Solar cooker consist of following-

1. Reflector: it reflects the rays that do not fall normally so that more and more rays enter the solar cooker. Concave reflector type cookers achieve a higher temperature by using mirrors to focus the rays of the sun.
2. Glass: It allows infrared rays to enter and rays get trapped and the temperature is maintained in the solar cooker.
3. Black color: A black color is a perfect absorber of heat, the sun rays falling on the reflector are reflector are reflected and the glass sheet allows them to enter but does not allow them to escape.

Inside it four bowl can be kept at a time in which we can make dal, rice, khichdi, etc.

Limitations:-

1. It cannot be used to bake, fry or make chapattis.
2. It is time consuming.
3. It cannot be used at night.
4. It cannot be used during rainy or humid weather.

Advantage of solar cooker:-

1. It is ecofriendly.
2. It saves fuel.
3. Nutrients value of food is retained.
4. It is free of cost as no fuel is used.

ii. Solar water heater:- It contains an insulated box, painted black from inside. In it, copper tubes are placed in the form of coils. Tubes are also painted black from outside. The box is covered with a glass sheet to prevent loss of heat. The two ends of the tube are joined to a storage tank. Fresh tap water enters the tank through pipes and then it flows through a copper tube in box and when flowing through a tube, it gets heated up and is collected at the top of the tank as density of hot water is always less as compared to that of cold water.

iii. Solar cell:- Solar cells are devices which are made of silicon and they convert solar energy to electrical energy.

• Solar cells are made up of silicon.
• Silver is used to interconnect the solar cells to each other to form solar panel.
• Domestic use of solar cells is limited due to its high cost.
• A typical cell develops a voltage of 0.5 – 1V and can produce about 0.7W of electricity when exposed to the sun.

Uses of solar cells:-

1. Artificial satellites and space probes like Mars orbiters use solar cells as the main source of energy.
2. Radio and wireless transmission system or TV relay stations in remote locations use solar cell panels.
3. Traffic signals, calculator and many toys are fitted with solar cells.

Advantage of Solar cells:-

i. They have no moving parts, so requires little maintenance.

ii. They work quite satisfactorily without the use of any focusing devices.

iii. They can be set up in remote area where laying of a power transmission line is more expensive and not commercially viable.

iv. It is alternative source of energy.

v. It does not produce pollutions and does not harm environment.

Limitation of Solar cells:-

i. These devices are useful only at certain times during the day.

ii. They do not perform good work during rainy days.

iii. There is limited production of electricity by solar cells.

iv. They have high cost and low efficiency.

Geothermal Energy:- Geothermal energy is the heat of the earth and is the naturally occurring thermal energy found within rock formations and the fluids held within those formations.

Magma is formed when this heat melts the rocks. The rocks and hot gases are called magma.

Hot spots: The magma gets collected at some depths below the earth’s surface. These places are called ‘Hot spots’.

            When underground water comes in contact these hot spots, it changes into steam, which can be used to generate electricity.

Advantage:-

i. The cost of production would not be much.

ii. Tapping of this energy is practically better for commercial use.

iii. It can be operated round the clock.

iv. It is a renewable source of energy.

Limitation:-

i. There are very less regions of geothermal energy on the earth.

ii. Reaching in such hot spots is very difficult and costly.

Nuclear Energy:- A reaction in which the nucleus of an atom undergoes a change to form a new atom and releases an enormous amount of energy is called as nuclear energy. There are two ways to obtaining nuclear energy-

i. Nuclear fission:- It is the reaction in which energy is released when a bigger nucleus splits into two or more lighter nuclei. The energy released per fission is 200Mev. But fission reaction is uncontrolled due to which its energy cannot be used for constructive purpose but if we want to control it, we carry out the reaction in a nuclear reactor which is designed in such a way that controlled fission takes place.

Nuclear reactor:- It is a device which is used to control an uncontrolled fission. In it, the controlling rods are used which also absorb extra neutrons so that reaction does not occur as a chain uncontrolled reaction. These rods are made of cadmium and boron. Also, in it heavy water is used that slows down the speed of fast moving neutrons so that they can collude effectively with fuel rods. Coolant is used that absorbs the heat energy liberated due to the reaction. Most of the times liquid sodium is used.

Safety measures to be taken are as follows-

a. Lead containers must be used for keeping radioactive elements.

b. The workers must wear lead aprons and specially designed suits.

c. They are well insulated in a chamber made of glass.

Hazards of nuclear radiations-

a. Disposal of nuclear waste is a big problem.

b. There is a risk of accidental leakage.

c. It has high cost of installation.

d. Limited availability of nuclear fuel like uranium.

ii. Nuclear fusion:- It is the reaction in which energy is released when  two or more smaller nuclei binds in one bigger nucleus. This releases more energy than nuclear fission but this is an uncontrolled process.

Advantages of Nuclear energy:-

1. The alternative source of energy due to depletion of fossil fuels.
2. From a small amount of fuel, a large amount of energy is released.

Disadvantages of Nuclear energy:-

1. Risk of nuclear waste leakage.
2. High cost of setting up of nuclear plant.
3. Pollution of environment.

Environmental consequences of the increasing demand of energy:-

1. The combustion of fossil fuels produces acid rain and damages plants, crops, soil and aquatic life.
2. The burning of fossil fuels is increasing the amount of greenhouse gas, carbon dioxide in the atmosphere.
3. The construction of hydropower plants is a disturbing ecological balance.
4. Nuclear power plants are increasing radioactivity in the environment.

Difference between Nuclear fission and Nuclear fusion:-

Nuclear fission	Nuclear fusion
1.It involves breaking of heavy nucleus into lighter nuclei.	1.It involves the binding of two nuclei.
2.It is carried out by the bombardment of neutrons over a heavy nucleus.	2.It is carried out by heating an extreme temperature.
3.It is a chain reaction.	3.It is not a chain reaction.
4.It is a controlled process.	4.It is an uncontrolled process.
5.It produces an enormous amount of energy.	5.It produces more energy than nuclear fission.
6.Fission products are hazardous.	6.It does not cause pollution.

 The Sea Energy

1.Tidal Energy:-The energy produced due to high and low tides is called tidal energy. Tidal energy obtained from rising and falling of the level of sea water during tides.

Tide: The phenomenon of changing the level of the water of sea during the day is called tide.

Cause of tide:

i. Rotation of the Earth

ii. The gravitational pull of the moon

Tapping of Tidal energy:- Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at the opening of the dam converts tidal energy to electricity.

2.Wave Energy:- The kinetic energy possessed by huge waves near the seashore can be trapped in a similar manner to generate electricity. The waves are generated by strong winds blowing across the sea. A wide variety of devices have been developed to trap wave energy for rotation of turbine and production of electricity.

Limitation of wave energy:- Wave energy would be a viable proposition only where waves are very strong.

3.Ocean Thermal Energy:- The water at the surface of the sea or ocean is heated by the sun while the water in deeper sections is relatively cold. This difference in temperature is exploited to obtain energy in ocean-thermal-energy conversion (OETC) plant.

Ocean-thermal-energy conversion (OETC) plant: This is a device which is used to produce electric energy to use the heat form the difference of the temperature of top of ocean and the deeper section.

Tapping of Ocean Thermal Energy:- OETC plant is used for tapping this energy. This plant works when the temperature difference between the water at the surface and water at depths up to 2km is 293K (20⁰C) or more. The warm surface-water is used to boil a volatile liquid like ammonia. 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.

Limitation of Ocean Thermal Energy:-

i. The difference in temperature of the top and deeper section should be 20⁰C.

ii. Efficient commercial exploitation is difficult.