Monday 16 May 2022

Chapter 14


 Chapter 14



The best approach to save energy for future needs is its conservation. It deals with the judicious use of different energy sources so that they do not deplete too fast. Energy can be conserved by eliminating or reducing unnecessary use of energy and by enhancing efficiency in its production,

transportation and utilization. The un necessary use or waste of energy can be easily eliminated or moderated by changing our energy wasting habits. One can contribute to save a significant amount of gasoline and diesel by walking or riding a bicycle for shart (local) trips. In the heavy city traffic, cars

and bicycles move almost at about same speed. The leg powered bicycles are very useful for short distances of 5-8km. For long trips, people should use public transport (bus or train) whenever

possible. Energy and time can be saved by consolidating a trip to accomplish several taska together.One should drive at an economy speed and should turn the scooter or car engine off while gossiping with a friend on road. The engines should not be warmed for more than a minute. Keeping the engines properly tuned also reduces fuel consumption. These fuel saving tips are also helpful in reducing pollution of the environment. In order to avoid unnecessary use of electricity, we should tum off the lights and other appliances when not in use. In winter season, the hot water should not be let

running while bathing, washing clothes or dishes, brushing teeth and shaving. One should dress more wannily rather than using electric heaters to raise the room temperature. Such energy saving habits need to be encouraged.



The most important way for conserving energy is to increase efficiency in its production, trans-ission and utilizats





Efficiency in production refers to the amount of net useful energy produced in an energy pro-ducing industry. For example, in a coal based thermal power plant, coal is burnt to produce steam

for generating electricity. A large amount of coal energy is lost during conversion of chemical energy

into electrical energy. But if the coal is bumt more efficiently adopting advanced methods, the same amount of coal can be used to produce rather more electricity. The conversion efficiency of gas based thermal power plants is more than coal or oil based power plants. A considerable amount of

coal is lost during mining and its subsequent handling, The use of improved techniques of mining and coal handling can prove helful in saving a lot of precious coal which is otherwise lost. There is a need to increase energy production from renewable sources like water, wind, solar, biomass, geothennal

and tidal energy. Currently, the renewable sources are contributing only about 17 percent of the total energy being consumed in the world. The remaining 83 percent of energy is provided by non-renew-able fossil fuels. The renewable sources are quite promising alternatives to fossil fuels. An increase in energy production efficiency from these sources would definitely reduce the pressure on ex-

haustible fossil fuels. In the developing countries, the hydroelectric power potential has not been

adequately tapped. It has been estimated that the to hydroelectricity potential of India is about 4x10"KW, but only 11 percent of this potential is being utilized. There are several untapped

potential sites in the mountainous regions of the country. Most of these sites are suitable for con-struction of small scale hydroelectric power stations. Installation of more small scale power plants can increase electricity production.


Wind energy is a cheap and clean source of energy. The improvements in design of wind machines have resulted in an increase in their power production efficiency, The wind power experts

are hopeful to achieve 35 percent efficiency with further development of this technology. The stud-ies conducted by the United States Department of Energy and World Bank highlight that India has a great potential for wind power. It is estimated to be around 20000-25000 MW. At present, the

installed capacity of wind energy is only SSOMW. The development and use of wind energy need to be encouraged for conserving non-renewable energy sources. Similarly, in solar thermal power

systems, about 22 percent of the energy that hits the heat collector is converted into electrical energy. Different countries are making efforts to develop more energy efficient and cost effective solar cells. In rural areas, firewood is a major source of energy. But it remains a renewable source as long as e use it in a sustainable manner. The ever increasing demand of firewood has resulted in

a large scale deforestsation, floods and soil erosion. In order to conserve this source, a massive afforestation drive is very essential. The pressure on forest sources can also be reduced if the use

of biogas is promoted. In addition to production of gas, biogas plants also produce very useful manure. Liquid fuels such as ethanol and methanol prepared from biomass and oil produced by

certain plants have been successfully tested as alternate fuel for internal combustion engines. The development of more energy efficient technology could play a key role in enhancing production

efficiency of different renewable sources.



Energy can be saved by insatallation of congeneration units (Fig 14.1). Congeneration involves used waste or left over steam. In a thermal power plant fossil fuel in burnt to produce steam from water. This steam turns the turbine for generating electricity. Then this steam is coolded and pumped

back to the boiler. In a congeneration unit this leftover steam is used to do some useful work before cooling. It can be used for cooking, space heating or for operating industrial machinery, The electric-ity generated from power plants is supplied to different areas by electric supply lines. For this pur-

pose, step up and step down transformers are used for increasing or decreasing the voltage. During this transmission a fraction of the power may be lost due to technological factors, In developed

countries, only about 7 percent of the electric power is lost during transmission. But in India, the

transmission losses are exceedingly high. About 20-23 percent of power is lost during distribution.The transmission losses are largely due to theft of the power. It can be prevented by 

strict implementation of the rules, besides adopting ethical approach, The transmission losses result-ing from technical factors can be minimized by using advanced type of energy- efficient transfonmers and high-tech-conductors. Recently the technology for transmission of power at high voltage in its

DC Girect current) from has been developed. This has proven very helpful in minimizing the trans-mission losses. These innovative techniques can be incorporated in future plans.



Most of the energy harnessed from different renewable and non-renewable sources is utilized in industries, transport vehicles, domestic services and agriculture, An increase in energy utilization effi-ciency in these sectors could enable us to do more work with less amount of energy. In India,

industry (paper, plastic, cement, textile, fertilizer, pharmaceutical, chemical, food processing and metal

industries) alane consumes about 50 percent of the total energy. In industrial sector, lot of energy can

be conserved by using energy efficient machinery and adopting energy saving processes. The timely maintenance of heavy industrial machinery results in its better energy utilization efficiency, Roughly about 66 percent of the total electricity consumed in the world is used for running electric industrial motors. The power saving improvements in the structural design of motors could minimize the total

electricity consumption, Recycling of certain substances such as glass, plastics, paper, discarded aluminium cans etc. is also helpful in reducing the use of electricity. For example, a large amount of electricity is consumed for production of aluminium worldwide. If recycled aluminium is used, this

electricity consumptiom can be reduced by 90 percent. Owing to advanced technology, Japan is making most efficient utilization of energy in industries. Countries like West Germany, Italy, Spain and France also have high efficiency in industrial utilization of energy.


Transport is the second largest energy consuming sector after industries. It accounts for about 22 percent of the total energy consumption in India, About 40 percent of petroleum products are

utilized in transport sector. The number of automobiles is increasing day by day. The total mmmber of automobiles in the world was 520 million in 1999 and it is expected to increase one billion by 2018.The increasing number of vehicles has led to a rapid rise in demand of gasoline and diesel fuels. The

energy utilization efficiency in automobiles has been significantly increased by improving aerodynamic

designs and fuel efficiency of enginees. Automobile companies like Honda, Mercedes, Tata, Ford,Tyota, Suzuki, Fiat etc. have developed several fuel efficient models of different automobiles. Du-rable and light weight material is used of fabrication. The engines that can run on natural gas and

rechargeable batteries have been developed. Efforts are also being made to use hydrogen as a fuel for automobiles. Alcohal fuels like methanol and ethanol are much cleaner than gasoline. These can be prepared from biomass sources and are already in use. An efficient public transport syste, using buses and trains can reduce use of private vehicles by people. In addition to saving of energy, this would reduce pollution too.


Energy can also be conserved at home and farm. The use of standard energy efficient appli-ances such as refrigerators, air conditioners, freezers, washing

 machines, cloth dryers, mixer-grinders, ovens, hot water geysers, water pumps, water coolers, electric generators, televisions

etc. can save lot of energy. The energy efficient models of these appliances may cost slightly more but these products are more useful on a long term basis, Proper maintenance of agricul-tural machinery such as pump sets, electric motors, diesel engines, combines, tractors, auto-matic loaders, power operated sprayers etc. is very necessary to minimize waste of energy.Compact fluorescent light tubes consume only 25 percent of the electricity used by incandes-cent bulbs. Similarly, in the rural areas the use of improved chullahs is moer beneficial than the

traditonal chudlahs. In improved chuliahs, firewood is burnt more efficiently and a chimney is

used to eliminate smoke, The energy utilization efficiency of an improved chullah is 10-15 petcent more than a traditional ‘chullah’. In countries with cold climate, a large amount of en-

ergy is needed to heat residential and commercial buildings. A lot of energy can be saved if the necessary energy saving features are incorporated in the structural design of these buildings.

Efforts are also being made to use nanotechnology for enhancing efficiency in utilization of en-ergy. Nanotechnology deals with use and making of extremely small sized devices. The size ranges between 1 nanometer to 100 nanometer. One nanometer is equal to one billionth of a meter. Per capita utilization of an energy source depends upon its price also. Obviously, the low

price results in high consumption rate. A large amount of energy can be saved from unnecessary use or waste by people if a rational pricing policy is adopted. There should be incentives for

consumers who use the energy sources more efficiently. The people should be made aware about the judicious use of energy sources and protection of environment.



Petrol and diesel are two important petroleum products that are most widely used as fuel in automobiles. Theer has been a rapid rise in the demand of these non-renewable fuels due to ever

increasing number of automobiles. The long tenn emission of pollutants released by automobiless has caused pollution of the environment. This has necessitated a search for alternative fuels for motor vehicles, In this concern hydrogen, alcohol and fuel cells are being considered as promising alterna-tive sources of energy in future.



It occurs in trace amounts in nature. But it can be produced by electrolytic, thermal or pho-tolytic decomposition of water. In its gaseous state, hydrogen has a very low density. Hence, large

sized containers are required for its storage. In order to overcome this difficulty. It is nommally stored

in liquid or solid form. Liquid hydrogen is called as cryogenic hydrogen. It is stored in specially designed storage tankers. Hydrogen can be used as a fuel in specially designed automobile engines

and fuel cells. In its liquid form, it is used as a fuel in space ships. It can also be used to produce other fuels. For example, it reacts with carbon monoxide in the presence of a heated catalyst to form methanol. When burnt with pure oxygen, hydrogen yields only water vapours and no pollutants are

emitted into the atmosphere. The calorific value (150 KJ per gram) of hydrogen is much higher than

that of other fuels like petrol, diesel, ethanol etc.


The automobile companies are trying to develop cars in which liquid hydrogen produced by solar electricity could be used as fuel. The other serious problem is that hydrogen is a highly explo-

sive gas. An explosion of a storage tanker or transport tanker may cause a serious loss of life and property. The technology to use hydrogen as a source of energy is in its developing phase, Hydrogen is being considered as an important fuel source for future use.



Ethanol and methanol are two important alcohols that can be used as liquid fuel substitutes for petrol (gasoline) and diesel, Both of these alcohols can be produced from biomass which is a renew-

able source of energy. Liquid ethanol (ethyl alcohol) is also called as grain alchohol. It is a clear,colourless liquid with a characteristic odour. It can be produced from a variety of sugar and grain ctops by process of fermentation and distillation. These crops include sugarcane, sugar beets, pota-toes, sorghum, corn etc. Fermentation refers to the production of ethyl alcohol and carbon dioxide

from sugar present in different substances by an action of yeasts.


Methanol (methyl alcohol) is also known as wood alcohol. It can be produced from wood, agri-culture wastes, garbage, sewage sludge, coal and natural gas. These alcohols can be burnt as fuels both in light and heavy automobiles. Use of pure ethanol or methanol as a fuel nceds some modification in the conventional engines. However, gasohol (a mixture of gasoline and 10-23 percent ethanol) can be ditectly used as a fuel in conventional gasoline engines. Similarly, diesel can be mixed with 15-20 percent methanol to from Dieshol that can be used as a substitute for regular diesel fuel. Countries like Brazil and Zimbabwe have already started the use of gaschol as a liquid fuel for automobiles.


Ethanol and methanol burn more cleanly than gasoline and diesel. They release fewer air polhut-ants. But currently, these alcohols are more expensive than fossil fuels. Researches are trying to

develop more efficient production techniques and special type of engines for these alcohols. Techno-logical improvements could bring their costs down in future.



A fuel cells is an electrochemical device that generates electricity directly from chemical energy.

It consists of two electrodes which are separated by an electrolyte. Several types of fuel cells having different operating temperatures have been developed. A fuel cells looks like a battery but it does not store chemical energy. Hydrogen is fed into it as a fuel at anode (fig 14.2).


Oxygen is fed into it at cathode. In the fuel cell, these gases react to produce water and elec-tricity. Fuel cells have very high energy efficiency because no combustion is involved and chemical

energy is directly converted into electricity. Fuel cells can be used to run automobiles by replacing internal combustion engines with traction motors that can run on electricity produced by fuel cell.Electricity generated by fuel cells can also be used for several other purposes. They could prove vety helpful in providing electricity to commercial buildings, hospitals, airports and military stations located in remote areas of a country. Fuel cells are modular structures and can be given different shapes as per need. They do not cause any serious pollution problem. The current costs of produc-ing electricity by fuel cells are quite high. After further research and development, fuel cell technology

could become available for widespread use in future.



(A) Very short answer type questions (1 mark each) :

1, What do you mean by conservation of energy?

2. What is the impact of increasing demand of firewood?

3. Name two liquid fuels that can be prepared from biomass.

4, Whatis the significance of energy efficient appliances at home?

5. What is nanotechnology?

6. How many nanometers are there in a meter?

7, Give the reason for increase in demand in petrol and diesel.

8. Whatis cryogenic hydrogen?

9. Which chemical is known as grain alcohol?


(B) Short answer type questions (2 marks each) :

1. Howcan we avoid unnecessary use of electricity?

2. Whatis congeneration?

3. Howcan India increase its hydroelectricity potential?

4, Suggest two ways for conserving firewood.

5. What are the reasons for excessive electricity transmission losses in India?

6. Name any four electric appliances used at home.

7. What is fermentation?

8. Whatis fuel cell?


(C) Short answer type questions (4 marks each):

1, Mention some fuel saving techniques.

2. What should be done to minimize the electricity losses during transmission?

3. How can energy be saved at home and farm?

4. Write a note on production and storage of hydrogen.

5. What are different limitations of hydrogen as a source of energy?

6. Differentiate between gasohol and dieshol.


(D) Long answer type questions (5 marks each):

1. Discuss the importance of efficiency in production for conservation of energy.

2. How can energy be conserved in industry and transport sectors?

3. Explain the structure and working of a fuel cell.

4, Write about production, potential and advantages of alcohols as future soutce of energy.