Chapter 14
CHAPTER NO.14 CONVERVATION OF ENERGY
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.
CONSERVATION OF ENERGY SOURCES
The most important way for conserving energy is to
increase efficiency in its production, trans-ission and utilizats
EFFICIENCY IN PRODUCTION
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.
EFFICIENCY IN TRANSMISSION
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.
EFFICIENCY IN UTILIZATION
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.
FUTURE SOURCES OF ENERGY
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.
HYDROGEN
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.
ALCOHOL
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.
FUEL CELLS
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.
EXERCISE
(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.
