CBSE Class 10 Science Chapter 14 Sources of Energy

Class Notes of Ch 14 : Sources of Energy

Class 10th Science

Sources of Energy

      Topics: 

• Introduction
• Renewable and Non-renewable Sources of Energy
• Conventional Sources of Energy
• Fossil Fuels
• Coal, Petroleum, Natural Gas
• Hydro Power Plant
• Thermal Power Plant
• Improvements to Conventional Sources of Energy
• Bio-Mass
• Wind Energy
• Non-conventional Sources of Energy
• Solar Energy
• Tidal Energy
• Wave Energy
• Ocean Thermal Energy
• Nuclear Energy
• Environmental Consequences

Introduction

We use energy for various activities - Our vehicles run using petrol/diesel. When we cycle we use our muscular energy. We use electricity/electric energy for all our lighting in our houses and roads. In this chapter, we will study about 'Sources of Energy'.

Renewable and Non-renewable Sources of Energy

• Sources of energy that will get depleted someday are called Non-renewable sources of energy. Eg: Fossil Fuels, Petroleum
• Sources of energy which will never exhaust or can be regenerated/reused again and again are called renewable sources of energy. Eg: Solar Energy, Wind energy.

Conventional Sources of Energy

Conventional sources of energy are those which are being used for a long time now. They are generally non-renewable. Let now study the following sources of energy.

• Fossil Fuels
  • Coal
  • Petroleum
  • Natural Gas
• Hydro
• Thermal
• Wind

Fossil Fuels

• Fossil fuels are formed by natural processes of decomposition of dead and buried  plants, animals and other organism.
• They got buried under oceans and layers of earth many millions of years ago and with time, high pressure and high temperature they formed fossil fuels.
• The fossil fuels are found in mines.
• Fossil fuels are considered as non-renewable sources of energy. Although they are naturally formed by decomposing organisms and this process is always continuous, they are used at a much faster rate than they get formed. If they are used at such alarming rates, then they would get depleted very soon. So, it would be wise to use them sparingly and economically.
• Fossil fuels contain high percentages of carbon and mainly include coal, petroleum and natural gas.

Coal, Petroleum, Natural Gas

Coal

• In earlier times, coal was used to heat homes, industrial application is industries and factories, power locomotives
• Coal is very commonly many industrial applications to produce heat energy and locomotion.
• Coal is used to operate furnaces for melting metal ores.
• They are used to run internal combustion engines.

Petroleum

• Petroleum is again a carbon-rich compound formed by the decomposition of diatoms.
• Petroleum products are predominantly used to run automobiles.

Natural Gas

• It is made of methane (carbon) and is lighter than air.
• It is highly inflammable.
• It is used extensively as cooking gas.

Disadvantages of using Fossil Fuels

• Air pollution: Burning of fossil fuels generate a lot of chemicals like oxides of sulfur, carbon and nitrogen and release it into the atmosphere.
• Acid Rains : These chemicals fall back on earth as acid rain. They are very detrimental to natural and built environments.
• Greenhouse Effect and Global warming : Burning of fossil fuels release gases like carbon-di-oxide which trap the heat in the atmosphere without releasing it and causing temperatures to increase steadily.

Hydro Power Plant

• Dams are constructed at heights to obstruct the flow of water and store it. The stored water has Potential Energy.
• Water stored in heights now is allowed to flow to low levels. The potential energy is converted to kinetic energy and moves the turbines.
• Electricity is produced.
• This is called Hydroelectricity because the potential energy of water which is stored at elevated heights is converted into kinetic energy of flowing water which in turn is converted electricity
• It is a renewable source of energy, since rainfall comes over and over again.
• Most of the electricity in India is generated in this method. Since there are not many natural waterfalls, dams are constructed to store water at heights and then allowed to fall and this energy is used to move turbines and thereby generate electricity.

Thermal Power Plant

• Fossil Fuels such as coal are burnt
• They are used to heat water to produce steam
• The steam from these moves turbines
• The movement of these turbines generate electricity
• This is called a Thermal Power Plant because the heat energy obtained from burning fossil fuels is used to generate electricity.
• Thermal power plants are generally found near coal and oil fields.

Improvements to Conventional Sources of Energy

Biomass and Wind energy are conventional sources of energy, but a lot of technology has been deployed in using these energies such that they are economical, environment friendly and more usable.

Bio-Mass

• Plant and animal wastes (dung), vegetable wastes, sewage are decomposed in absence of oxygen to produce Biogas
• Since the source of these fuels is animal dung, the source of these fuels is called Biomass.
• It is commonly called Gobar-gas

Biogas Plant

• Mixing tank : Cow dung and water is mixed together to form slurry which is fed into the mixing tank.
• Digester : The slurry is passed on to the digester which is a completely sealed chamber with no oxygen. Here anaerobic decomposition of slurry takes place.
• Gas tank: The anaerobic decomposition releases gases such as methane, carbon-di-oxide, hydrogen and hydrogen sulphide which are collected in the Gas tank and drawn out through the gas outlet

Advantages of Biogas	Disadvantages of Biogas
·         Since India has a large rural population and large live-stock population, this fuel is easily available. ·         Excellent fuel with reasonable heating efficiency ·         Burns without smoke ·         Does not leave residue ·         Slurry residue can be used as a manure ·         Environment friendly	·         Less heating efficiencycompared to other sources. ·         Releases gases (carbon, hydrogen, hydrogen sulphide, methane) which can corrode metal parts of the biogas plant itself. ·         It cannot be constructed easily because of the inputs are cow dung (and other wastes) which are available mostly in rural parts only.

  

Wind Energy

• In areas which are very windy, windmills are erected.
• A windmill consists of a fan-like structure erected on a strong standing support at a considerable height.
• The strong wind moves the wings of the windmill and this turns the turbines of the electric generato This mechanical energy is converted to electrical energy.
• Since the output of a single windmill is very small, many such windmills have to be erected in a carefully chosen place where there is consistent blowing of winds of atleast 15km/hr. This is known as a wind energy farm which are generally large (2 hectares of land)

Advantages of Wind energy	Disadvantages of Wind energy
·         It is environment friendly. ·         Renewable source of energy ·         Only construction expense is involved, but the maintenance (or recurring cost) is less	·         Initial establishment for construction is high. ·         Also, a lot of open area for wind energy farm is required. ·         Cannot be established everywhere because of requirement of open space an also where winds blow at greater that 15km/hr for most of the year.

Alternate/Non-Conventional Sources of Energy

With growing population and industrial needs, there is a need to look for sources of energy which is environment friendly, economical, renewable and effective.

• Solar Energy
• Energy from the sea
  • Tidal Energy
  • Wave Energy
  • Ocean Thermal Energy
• Nuclear Energy

Solar Energy

• Sun's heat which falls on the earth can be harnessed for various heating and lighting purposes.
• Most of the sun's heat is absorbed is the atmosphere.
• Only a very small portion reaches the earth and it is this energy that can be harnessed for energy purposes.
• A black surface absorbs more heat than a white surface.
• This property is used in Solar cookers, Solar water heaters and Solar cells.

Working Solar Cooker

• It has a reflective mirror of highly polished glass so that the sun's light is focussed into the system.
• Then this is converted to heat energy. The black surface absorbs more heat.
• The heat is trapped in the sealed glass/plastic bag such that the heat does not escape.
• The food gets cooked because of this heat.

Advantages of Solar energy	Disadvantages of Solar energy
·         Renewable source of energy ·         Environment friendly ·         Easy to install and use.	·         It cannot be used on cloudy and rainy days.

Working of Solar cell/Solar panel

• It converts solar energy into electricity.
• Since sun light will not be available during cloudy days, this cell can be used when there is sunlight to store the energy as electricity.
• Multiple solar cells put together form a solar panel and enhances quantity of electricity
• Works on the principle of 'Photovoltaic effect'.
• Solar cells are used in calculators, torches, traffic signals, TV and radio relay stations etc

Advantages of Solar cells	Disadvantages of Solar cells
·         Renewable source of energy ·         Environment friendly ·         Easy to maintain. ·         Very useful in remote locations where there is a power crisis	·         Initial setup cost is high.

Tidal Energy

• The rise and fall of sea level caused by the gravitational forces exerted by the Sun, Moon and the rotation of the Earth is called a Tide.
• A wave is not a Tide.
• On a single day, 2 high tides and 2 low tides are usually experienced by an ocean.

Electricity generation using Tidal Energy

• Generally dams are constructed towards narrow openings of sea.
• When there is a high tide, the increase in water in the sea is stored in the dam. The estuary has lower level of water. Water flows from sea to estuary (along the direction shown in the figure) and the turbine rotates.
• When there is a low tide, the estuary has higher level of water. Water flows from estuary to sea (along the direction shown in the figure) and the turbine rotates.
• As turbine rotates, electricity is generated.

Advantages of Tidal Energy	Disadvantages of Tidal Energy
·         More reliable (more than solar/wind) ·         Renewable ·         Low maintenance cost	·         Initial cost is very high ·         Limited power generation because tides happens only twice a day. ·         Not environment friendly because construction of dams could harm aquatic plants and animals.

Wave Energy

• Wave is caused by the strong wind blowing on the surface of the ocean.
• Kinetic energy of waves is used to generate electricity.
• A structure(as shown in the figure) is erected in the sea which has a piston attached to a turbine.
• The other end of the piston touches the ocean water.
• When there is a rising wave, the level of water increases, pushing the piston upwards. The piston is in turn connected to a turbine which rotates and electricity is produced.
• When there is a falling wave, the level of water decreases, pushing the piston downwards. The piston is in turn connected to a turbine which rotates and electricity is produced.



Advantages of Wave Energy	Disadvantages of Wave Energy
·         More reliable (more than solar/wind) ·         Renewable ·         Low maintenance cost	·         Initial cost is very high ·         Not environment friendly because setting up of a plant could harm aquatic plants and animals.



Ocean Thermal Energy
• The surface of the ocean is at a higher temperature than the layers below. This is because of the sun's heat warms up the upper layers of the sea.
• This temperature difference is exploited to generate energy
• A minimum temperature difference of 20 degrees C is needed between water at the surface and at a depth of about 2 km.
• This requires Ocean Thermal Energy Conversion plants which converts ocean thermal energy to electricity.


Ocean Thermal Energy Conversion Plants
• The water at surface of the ocean which is at higher temperature vaporizes liquid ammonia.
• The vapour ammonia now moves the turbine which generates electricity.
• The vapour ammonia then, is condensed using the water at the bottom layers of the ocean. It now again becomes liquid ammonia.
• This is again heated by the heat from the top layers and the process continues.

Advantages of Ocean Thermal Energy	Disadvantages of Ocean Thermal Energy
·         More reliable (more than solar/wind) ·         Renewable ·         Low maintenance cost	·         Initial cost is very high ·         Not environment friendly because construction of such plants could harm aquatic plants and animals.



Nuclear Energy
• Atom consists of nucleus and electrons in orbits.
• The nucleus consists of protons (positively charged particles) and nuetrons (nuetrally charged particles)
• Energy is obtained from the nucleus in the following methods
• Nuclear Fusion: Breaking a heavy nuclei into 2 or more smaller lighter nuclei
• Nuclear Fission : Combining 2 lighter nuclei to form a heavy nucleus
  • Uncontrolled chain reaction : In an uncontrolled nuclear fission, a heavy nucleus in bombarded with a neutron. It splits into lighter nuclei releasing 2 or more neutrons. Each neutron again bombards nuclei of atom and splits further and further. The neutrons and thereby the fission reaction exponentially increases. Eg : Atom bomb
  • Controlled chain reaction : In an controlled nuclear fission, a heavy nucleus in bombarded with a neutron. It splits into lighter nuclei releasing 2 or more neutrons. But in this case, except one neutron all the other neutrons are absorbed. So, only one neutron is left. This single neutron again bombards nuclei of atom and splits further and further. Again only one neutron is left behind and the others are absorbed. So, the reaction is controlled. Eg: Nuclear generator.
  • In a nuclear generator, nuclear energy is harnessed in a controlled manner to generate electricity.

• Advantages of Nuclear Power Plant	Disadvantages of Nuclear Power Plant
  ·         Energy is released is extremely large. ·         The amount of initial fuel required is very small.	·         The products used and by-products generated are radioactive and extremely harmful for man. ·         Installation cost of nuclear plant is very high.

  
  
  Environmental Consequences
  • Some sources of energy (coal, petroleum) are non-renewable cause harm to the environment.
  • In other cases, though they do not cause harm to the environment, the setup and maintenance cost (windmills, solar energy)is very high
  • So, there is continuous research going on to use energy which is (i) environment friendly (ii) renewable (iii) economical (iv) efficient.
   
• SCIENCE Revision Notes
  
  Chapter:01  Chemical Reaction & Equation
  Chapter:02  Acid Base & Salt
  Chapter:03  Metals & Non Metals
  Chapter:04  Carbon & its Components
  Chapter:05  Periodic Classification of Elements
  Chapter:06  Life Processes
  Chapter:07  Control & Coordinates
  Chapter:08  How do Organisms Reproduce
  Chapter:09  Heridity & Evolution
  Chapter:10  Light Reflection Refraction
  Chapter:11  The Human Eye & the Colourful World
  Chapter:12  Electricity
  Chapter:13  Magnetic Effect of Electric Current
  Chapter:14  Source Of Energy
  Chapter:15  Our Environment
  Chapter:16  Management of Natural Resource
  
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