Notes on Sources of Energy Class 10 Science 14

These notes are useful for SEBA as well as CBSE students. In this article, we have included every important point, so that you can attempt any MCQ as well as any question of your Board Exam from this chapter. Here we have given NCERT notes on Sources of Energy Class 10 Science 14, written in simple English so that you do not rely 100 % on NCERT Books. According to new SEBA Exam Pattern, MCQ Questions for Class 10 Science  Carries 45 Marks.

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Notes on Chapter 7: Control and Coordination

Sources of Energy:

Energy

The capacity or ability to do work is energy. Energy exists in many forms. Energy can never be created or destroyed. It just changes from one form to another.

Sources of energy:

Sources of energy are the substances or natural resources from which we obtain energy for various activities.

Examples of sources of energy: coal, petroleum, natural gas, sunlight, wind, flowing water, biomass, and nuclear fuels.

What Is a Good Source of Energy?

A good source of energy has the following properties:

• It should produce a large amount of heat energy per unit mass or volume.
• It should be affordable and economical to use.
• It should be easy to store and transport.
• It should be easily accessible.

What are the characteristics of a good fuel, or what is good fuel?

A good fuel should have certain characteristics. These are —

(i) A fuel should have a high calorific value.
(ii) It should be economical.
(iii) It should have a suitable ignition temperature. (Ignition temperature is the temperature at which a fuel starts to burn. The ignition temperature of a fuel should neither be very high nor very low.)
(iv) It should be easy to store and transport.
(v) It should be easily available in sufficient quantities.
(vi) It should be eco-friendly.

What is a Turbine?

A turbine is a rotatory mechanical device that converts the energy of a moving fluid (such as water, steam, or wind) into mechanical energy by rotating its blades. The rotating turbine is connected to a generator, which converts this mechanical energy into electrical energy.

How Do We Generate Electricity from Different Sources?

Most power plants generate electricity by using a common principle. A source of energy is used to rotate the blades of a turbine. The turbine is connected to an electric generator, which converts the mechanical energy of the rotating turbine into electrical energy. The only thing that changes from one power plant to another is the way we spin the turbine blades.

For example:

• In thermal power plants, steam produced by burning fossil fuels rotates the turbine.
• In hydroelectric power plants, flowing water rotates the turbine.
• In wind power plants, moving air rotates the turbine.

Different Sources of Energy

Energy sources can be classified in two types – a) Renewable , b)Non-renewable

a) Renewable sources of energy: 

The sources of energy that can be replenished or regenerated by nature are called renewable sources of energy. They are freely available in nature.

Examples of Renewable Sources of Energy:

• Solar energy.
• Wind energy.
• Hydro-energy.
• Geothermal energy.
• Ocean energy.
• Biomass energy.

Advantages 

• They do not create pollution
• They are easily available

b) Non- renewable energy sources

The sources of energy that will get depleted someday and cannot be regenerated quickly once used up are called exhaustible or non-renewable sources of energy.

Examples: Coal, petroleum, natural gas, and nuclear fuels.

Disadvantages

• It affects the environment by producing pollution
• They are available in limited amount in nature

Conventional Sources of Energy

Conventional sources of energy are traditional sources of energy. These sources have been used for many years and are available in limited quantities. These are non-renewable sources of energy. Examples: Fossil fuels, hydroelectric energy, biomass, biogas

What is Non-conventional Source of Energy?

The sources of energy that are recently come into use are known as ‘non-conventional sources of energy. These sources are renewable sources of energy. Non-conventional Sources of Energy are naturally replenished and cause less pollution.

Examples:

• Solar energy
• Wind energy
• Biomass energy
• Tidal energy
• Geothermal energy
• Ocean thermal energy
• Nuclear energy

Fossil Fuels: Coal and Petroleum

Fossil fuels were formed millions of years ago from the remains of dead plants and animals buried deep under the earth. There are only limited reserves available of fossil fuels. The fossil fuels are non-renewable sources of energy. Examples: Coal, Petroleum, Natural gas etc.

Disadvantages of burning fossil fuels

• Burning fossil fuels causes air pollution.
• Burning fossil fuels releases acidic oxides of carbon, nitrogen, and sulphur. These oxides cause acid rain, which affects our water and soil resources.
• Burning fossil fuels also releases carbon dioxide, which contributes to global warming.
• Their reserves are limited. If we keep using them at the current rate, they will get exhausted soon.

Thermal Power Plants

A thermal power plant is a plant that converts heat energy into electrical energy. In a thermal power plant, large amounts of fossil fuel are burnt to heat water and convert it into steam. This high-pressure steam is used to rotate the turbine to generate electricity.

The term ‘thermal power plant’ is used since fuel is burnt to produce heat energy, which is then converted into electrical energy.

Why Are Thermal Power Plants Located Near Coal or Oil Fields?

The transmission of electricity is more efficient than transporting coal or petroleum over the same distance. That is why most thermal power plants are set up near coalfields or oil fields.

Hydropower Plants

A hydroelectric power plant generates electricity from flowing water. ‘Hydroelectricity’ means electricity generation from water.

Hydropower plants convert the potential energy of stored water into electricity. In order to produce hydel electricity, high dams are built across rivers to block the flow of water and collect it in a large reservoir. Water from the reservoir is then allowed to fall through pipes onto the blades of a turbine at the bottom of the dam. As the water falls, its potential energy changes into kinetic energy, which turns the turbine and generates electricity.

Hydropower is a renewable source of energy. In India, hydropower plants meet about a quarter (25% ) of our total energy needs.

Problems with building large dams

• Dams can be built only in a limited number of places, usually hilly areas.
• Large areas of agricultural land and human settlements get submerged under reservoir water.
• Submerged vegetation rots under anaerobic condition and releases methane, a greenhouse gas.
• Displaced people often face problems of proper rehabilitation. The Tehri Dam on the river Ganga and the Sardar Sarovar project on the river Narmada are well-known examples of such disputes.

Improving the Technology of Conventional Sources

As our demand for energy keeps rising, scientists keep improving the technology used for conventional sources so that we use them more efficiently.

Bio-mass

Biomass is the organic matter derived from plants and animals that can be used as a source of energy. Examples of biomass: wood, cow-dung cakes, agricultural/vegetable waste, and domestic sewage.

The energy obtained from biomass is called biomass energy. Such energy is also known as Bio-energy.

However, plain bio-mass does not produce much heat and gives off a lot of smoke. To solve this, we convert bio-mass into better fuels.

Charcoal:

When wood is burnt with a limited supply of oxygen, water and volatile materials are removed. The solid residue left behind is charcoal. Charcoal burns without flames, produces less smoke, and has a higher heat-generation efficiency than wood. So, charcoal is better fuel than wood.

Bio-gas:

• Bio-gas is a mixture of gases produced by anaerobic decomposition of biomass in the absence of oxygen
• Biogas is a mixture of gases containing up to 75% Methane ($\text{CH}_4$), along with Carbon Dioxide ($\text{CO}_2$), Hydrogen ($\text{H}_2$), and Hydrogen Sulphide ($\text{H}_2\text{S}$)
• Since the starting material of Biogas is mainly cow-dung, bio-gas is popularly known as “gobar gas”.
• A biogas plant produces biogas. A biogas plant consists of a large tank or digester. In this, anaerobic micro-organism convert organic waste into biogas in the absence of oxygen.

Advantages of Biogas:

• Bio-gas is an excellent fuel because it contains up to 75% methane.
• It burns without smoke, leaves no ash-like residue,.
• Its heating capacity is high.
• It is also used for lighting.
• The leftover slurry is drained periodically and used as high-quality organic manure, as it is rich in Nitrogen and Phosphorus.

Wind Energy

Wind Energy: The energy which is obtained from wind is called wind energy.

Windmill: A windmill is a device that converts the kinetic energy of wind into mechanical or electrical energy. A windmill is used in a water-lifting pump. Windmills are also used to generate electricity.

Working of a Windmill

A windmill consists of large fan-like blades. These blades are erected very high on a rigid support. They are attached to turbines that rotate due to high wind speeds and generate electricity. 

Wind energy farm: A group of windmills is called a wind energy farm. A wind energy farm is used to generate electricity on a commercial scale.

Important Facts:

Denmark is known as the country of winds. India ranked fifth in harnessing wind energy for the production of electricity. The largest wind farm in India is located near Kanyakumari in Tamil Nadu.

Advantages of wind energy:

1. Wind energy is an environment-friendly source of energy.
2. It is a renewable source of energy.
3. It requires no recurring costs for production of electricity.

Limitations of wind energy

• Wind farms need places where wind blows for most of the year.
• The wind speed should be higher than 15 km/h to run the turbine.
• Wind energy farms requires large area of land.
• The initial cost of establishing wind energy farm is very high.
• A windmill needs a high level of maintenance.
• Wind farms require backup facilities to supply electricity when there is no wind.

Alternative or Non-Conventional Sources of Energy

As our lifestyles change and industries grow, our demand for energy keeps increasing. This has pushed scientists to look beyond conventional sources and explore newer, alternative sources of energy.

Solar Energy

The energy obtained from the Sun in the form of heat and light is called solar energy. The sun is the main source of energy for all living beings on this Earth. It is a renewable source of energy because it is naturally replenished and available in abundance.

Advantages of Solar Energy

• It is a renewable and inexhaustible source of energy.
• It does not cause air pollution.
• It is freely available in abundance.

Disadvantages of Solar Energy

• Solar energy is available only during the daytime.
• Its availability depends on weather conditions and is reduced on cloudy or rainy days.
• Solar panels and related equipment have a high initial installation cost.

What are Solar Energy Devices?

A device that uses the Sun’s energy directly to produce heat or electricity is called a solar energy device.

Examples of Solar Energy Devices

• Solar cooker
• Solar water heater
• Solar cell

Solar cooker and solar water heater

A solar cooker is a device which is used to cook food by utilizing the heat energy from the sun.

A black surface absorbs more heat than a white or shiny surface. Solar cookers use this idea by painting their inner surface black. Some solar cookers also use mirrors to focus the Sun’s rays and reach a higher temperature. A glass sheet covers the cooker, which traps heat inside through the greenhouse effect, just like glass traps heat in a car parked in the sun.

Solar cell :

A solar cell is a device which converts solar energy directly into electricity. Solar cells are usually made of silicon. They are widely used in calculators, satellites, street lights, traffic signals, etc.

Solar cell panel :

A single solar cell produces a small voltage of about 0.5 to 1 V and can produce about 0.7 W of power. A large number of such solar cells are combined in an arrangement called solar cell panel, which can supply enough electricity for practical use.

Advantages of Solar Cell Panels

• • They require very little maintenance because they have no moving parts.
  • They can be installed in remote areas where electricity supply is difficult.
  • It is ideal for remote or sparsely populated areas where laying power lines would be expensive.
  • Solar energy is renewable and inexhaustible.
  • Solar panels do not produce air or noise pollution during operation.

Limitations of Solar Cell Panels

• The manufacturing process of solar panels is very expensive.
• Making solar cells needs a special grade of silicon, which is scarce.
• Silver used for connecting the cells in the panel increases the overall cost.
• Their efficiency decreases during cloudy or rainy weather and at night.

Applications of Solar Cell Panels

In spite of their high cost and relatively low efficiency, solar cell panels are used in many important scientific and technological applications. Some common applications are:

• They are used as the main source of energy in artificial satellites and space probes, like Mars orbiters.
• They are used in radio and wireless transmission systems or TV relay stations located in remote areas.
• Traffic signals, calculators and many toys are fitted with solar cells.

Energy from the Sea

The following are most common ways of obtaining energy from the sea—
(a) Tidal energy.
(b) Wave energy.
(c) Ocean thermal energy.

Tidal energy

Due to the gravitational pull of the moon, the level of water in the sea rises and falls. This phenomenon is called high tide and low tide. This difference in sea levels gives us tidal energy.

Tidal energy is obtained by constructing a dam near the narrow openings of the sea. A turbine fixed at this opening of the dam converts tidal energy into electricity.

Limitations of Tidal Energy

• There are very few suitable sites available for construction of dams.
• The construction of dams and power plants is expensive.

Wave energy

• Waves are generated by strong winds blowing over the sea.
• Waves possess a lot of kinetic energy. Devices have been designed to trap this energy.
• This energy can be trapped near the sea shore to rotate a turbine and generate electricity.
• However, this method works only where waves are powerful enough, so its use is limited to specific coastal areas.

Ocean thermal energy

Solar energy stored in the oceans in the form of heat is called Ocean Thermal Energy (OTE). The process of harnessing the thermal energy of the sea is called ocean thermal energy conversion, and the devices used for this purpose are called Ocean Thermal Energy Conversion (OTEC).

The surface water of the ocean is much warmer than the water in greater depths, because the Sun heats up the surface water of the sea. This temperature difference can be used to obtained energy in an Ocean Thermal Energy Conversion (OTEC) plant. Such a plant works only if the temperature difference between the water at the surface and at a depths of about 2 km is 293 K (20°C) 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 the generator. The cold water from the depth of the ocean is pumped up and then condenses the vapour back into liquid.

Geothermal Energy

The energy obtained from the molten rocks in the deeper hot regions of earth’s crust is called geothermal energy.

• Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upward and trapped in certain regions called ‘hot spots‘.
• When underground water comes in contact with these hot spots, it turns into steam.
• Sometimes hot water from hot spot region finds outlets at the surface. Such outlets are known as hot springs.
• The trapped steam is carried through a pipe to a turbine and used to generate electricity.
• New Zealand and the United States already have several working geothermal power plants.

Nuclear Energy

The energy released during nuclear reactions that occur inside the nucleus of an atom is called nuclear energy.

Nuclear fission

Nuclear fission is the process in which the nucleus of a heavy atom splits into two or more smaller nuclei when it is bombarded with a low-energy neutron. This process releases a tremendous amount of energy.

Example of Nuclear fission:

²³⁵₉₂U + ¹₀n → ¹⁴¹₅₆Ba + ⁹²₃₆Kr + 3(¹₀n) + Energy

Einstein’s mass-energy equation: E = mc², where m is the mass difference and c is the speed of light in vacuum.

To put this in perspective, the fission of just one atom of uranium releases about 10 million times more energy than burning one atom of carbon from coal. This is why nuclear power plants can generate a huge amount of electricity from a very small amount of fuel.

Nuclear fusion

Nuclear fusion is the process in which two or more light atomic nuclei combine to form a heavier nucleus and release an enormous amount of energy.

Deuterium + Tritium → Helium + Neutron + Energy

Or

²₁H + ³₁H → ⁴₂He + ¹₀n + Energy

This is the process that powers the Sun and other stars. A hydrogen bomb works on the principle of nuclear fusion.

Key Points

• It involves the combination of light nuclei.
• It releases more energy than nuclear fission.
• It requires extremely high temperatures and pressures.
• It is the primary source of the Sun’s energy.

Disadvantages of nuclear energy

• Safe storage and disposal of used nuclear fuel is a major challenge because radioactive waste continuously emits harmful radiation.
• There is a risk of accidental leakage of nuclear radiation, which can cause serious health and environmental damage.
• Setting up a nuclear power plant needs a very high initial investment.
• There is limited availability of uranium.
• It can be used for destructive purposes.

Difference Between Nuclear Fission and Nuclear Fusion

Environmental Consequences of Using Energy Sources

The following are the consequences of using different sources of energy:

1. Fossil fuels such as coal, petrol, and diesel, when burnt, cause air pollution and release greenhouse gases.
2. Construction of dams may destroy large ecosystems and create problems related to the rehabilitation of displaced populations.
3. Construction of heavy structures to harness wave energy and tidal energy may affect marine ecosystems and aquatic animals.
4. Nuclear energy produces radioactive waste, which is difficult to dispose of safely and may cause harmful effects on living organisms.

How Long Will an Energy Source Last Us?

Sources of energy that will get depleted someday are called exhaustible or non-renewable sources of energy.

Sources of energy that can be replenished or regenerated are called renewable sources of energy.

Renewable vs Non-Renewable Sources of Energy (At a Glance)