Chapter 13
CHAPTER NO.13 NON-CONVENTIONAL SOURCES
OF ENERGY
Non-conventional sources of energy include biomass,
solar, wind, ocean, hydel, geothermal and nuclear energy. Most of these sources
except for nuclear energy are inexhaustible and can be used
indefinitely. These are renewed by nature and are
also known as renewable energy sources. In comparison with fossil fuels, these
sources cause less pollution of the environment, With rapidly expanding human
population and ever increasing demand of energy, renewable sources are most
promising alternative energy sources for long term use in future.
BIOMASS ENERGY
Biomass includes wood, fast growing plants, cattle
dung and crop residues. It contains solar energy fixed in the form of chemical
energy by green plants through process of photosynthesis. It is
primarly used for cooking and heating. Biomass can
be used in its solid from or it can be changed to liquid or gas fuels, Firewood
can be changed into charcoal by partial burning, Cattle dung is used to make
rounded dung cakes. It can also be used to produce biogas that is a mixture of
gases espe-cially methane (60-70 percent), carbon dioxide, hydrogen and
hydrogen sulphide. Biogas is pro-duced by action of micro-organisms in a biogas
plant, For this purposes, cattle dung is mixed with
water and put inside an airtight container called
digester (fig. 13.1).
Under anaerobic conditions, the bacteria breakdown
the undigested plant material of cattle dung into biogas. The remaining solid
material is used as fertilizer for crops. Biogas can also be collected from
household wastes and industrial wastes, dumped and buried in the landfills.
Liquid fuels such as
methanol and ethanol can be prepared from biomass and may be used in engines. Some plants like Jatropha, belonging to the family Euphorbiaceae yield useful oil which can be used as fuel in diesel engines.
As mentioned in the previous chapter, about half of
the world population depends upon biom-ass as a primary source of energy. It
acts as an inexhaustible energy source if managed in a sustain-able manner. In
rural India, biomass is the most important source of energy. There are more
than
1,852 million biogas plants in India and potential
exists for millions more, Cultivation of oil yielding plants is also gaining a
momentum. There is a pressure on forest sources duc to increased demand of
firewood, Undoubtedly, the use of biomass decreases our dependence on fossil
fuels, but it also contributes to the problem of global warming by increasing
the level of carbon dioxide in the atmo-
sphere. This problem can be minimized if biomass
used is replaced by biomass regenerated. As in case of wood, other forms of
biomass like animal waste and crop residues also release oxides of
sulphur and nitrogen into the atmosphere. On burning biomass, a lot of
suspended particulate matter is produced. Cutting of trees for firewood also
leads to soil erosion and desertification, When biom-ass is bumt in traditional
‘chullahs’ or open fires, a large amount (80-90 percent) of energy is
dissi-pated into the environment.
SOLAR ENERGY
Solar radiation falling on the earth's surface is
most important renewable source of en-ergy. Every year, the earth receives
solar radiation equivalent to 1500 times the commercial energy consumption of
the world. But the problem is that unlike fossil fuels and nuclear en-ergy,
solar energy is not concentrated in localized areas. It is dispersed over the
vast surface
of the earth. In order to harness this energy, the
solar radiation is concenterated or trapped in a small area. This can be
achieved through passive solar heating or active solar heating. Pas-sive solar
heating is used to warm buildings. It makes the use of green house effect and
is the
simplest, cheapest, pollution and maintenance free
method for hamessing solar energy. Some radiation trapping structural features
are incorporated in design of the buildings. These in-
clude large sun facing glass windows for receiving
more solar radiation, a few or no north facing windows, walls and floors of
concrete or stone and insulated curtains to reduce loss of
heat during night. Passive solar heating can also be
done by adding a small green house to the building. Similarly, in a solar
cooker, the trapped heat energy is used for cooking food. The glass top and
reflector of the solar cooker concentrate solar radiation inside the box. In
order to absorb more energy, the inside of cooker is blackened and the cooking
vessel is placed on a metal sheet.
Active solar heating is used to heat water. It
involves the use of specially designed collection devices to concentrate solar
energy (fig. 13.2). A typical collection device consists of a coil of cop-per
pipe fixed to a blackened metal base in an insulated box. This box is covered
with glass.
The absorbed heat is transferred to the liquid
(water or antifreeze solution) or air inside the copper pipe. This hot
substance is then pumped to an insulated water storage tank. This system is
installed on the roof of building. It is more expensive than passive solar
heating system. Both these types of solar heating systems supply free energy
for warming buildings or heating water on sunny days. However, at night or on
cloudy days, this supply of energy is
not available.
Solar energy is used to produce electricity by solar
thermal electricity generation. This process involves use of computer-guided
mirrors that follow the sun for its optimum radiation. Trough-shaped mirrors
are used to concentrate solar radiation on oil filled pipes. The oil is heated
to 390°C and then
pumped through a water storage system. The heat released
from the oil changes the water into steam that turns a turbine to produce
electricity. In another type of arrangement, the solar radiation concen-trated
by a large array of mirrors is focused on a boiler mounted at the top of a
tower. The steam
generated in this boiler is used to turn a turbine
for producing electricity. Electricity can be directly produced from solar
radiation by using photovoltaic cells. These cells are made up of purified
silicon and smal] amount of other chemicals such as gallium arsenide or cadmium
sulphide. When sunlight falls on a photovoltaic cell, it emits electrons and
produces a small amount of electric current. In
order to increase the amount of electricity, a large
number of photovoltaic cells are coupled together
to form a solar panel. Simiarly, several solar
panels can be wired together to further enhance the generating capacity (Fig
13.3). These panels can be mounted on the rooftops. The electric current
produced by a photovoltaic cell is direct current
(DC) and can be converted into altemating current (AC) by using an electronic
converter. Solar cell technology has been used in satellites, electronic
watches, calculators, solar lanterns, street lights and water pumps. It is
quite promising for smaller
requirements.
All these different types of methods for harnessing
solar energy are being used in different countries. Efforts are being made to
develop more efficient and less expensive technology. India is
the third largest producer of solar cells and modules. More than 80 different
industrial companies are
engaged in marketing and manufacture of these items,
The arid land in the deserts of Rajasthan offers a great scope for hamessing
solar energy. A 30 MW Research and Developments cum demonstra-tion project at
Jodhpur in Rajasthan has already been sanctioned by the Government of India.
Two 100KW partial grid interactive solar photovoltaic power projects have been
commissioned in Uttar Pradesh. The Govemment is also providing partial
financial assistance for installation of solar power operated irrigation pumps
in different states. Solar energy has many advantages. It is renewable and
abundantly available in nature. Use of solar energy
causes no pollution of the environment. The only problem with this form of
energy is that it is not available at night and during cloudy days. It needs a
power backup system, The amount of solar radiation received by an area also
depends upon season
and geographical location.
WIND ENERGY
Warming of the atmosphere by solar radiation causes
movement of air, Energy obtained from this moving air is known as wind energy.
People have been using wind energy since 16th century. It
is harnessed by wind mills. A windmill consists of
movable blades mounted on a pole or a tower.Wind rotates the blades of a windmill.
The mechanical energy produced due to rotation of blades is
used to pump water and grind grains. The improved designs of windmills are also used to produce electricity. For this purpose, a small generator is attached with a windmill (fig. 13.4). Rotation of the
blades
drives the coil of the generator to produce electricity. The electricity
producing wind machines
are known as wind turbines, A single wind turbine
produces a small amount of electricity. In order to increase electricity
generation capacity, a number of wind turbines are installed in a large area
and are wired together. This sort of acrangement is known as a wind farm. An
ideal wind speed of 8.23
m per second is sufficient to run a wind turbine.
Wind farms can be erected in areas having such favourable wind conditions.
Under optimum wind conditions, an efficiency of 45 percent can be achieved. In
India, Gujarat and Tamilnadu are leading states in production of wind energy
due to
availability of fayourable wind conditions, A large
wind farm capable of producing about 38 MW of electricity has been installed at
Kaniyakumari. The wind power potential of India is estimated to be around 20000
MW.
Wind energy has certain important merits. It is a
renewable source of energy and does not cause any environmental pollution. Wind
turbines can be installed in remote areas where other sources of energy are not
available. At the same time, the area occupied by a wind farm can also
be used for other purposes. The major limitation of
wind energy is that wind machines can only be operated in areas having a
suitable wind speed. When the wind dies down, the wind turbines stop
working, It has been recorded that even at the best
sites, the wind turbines work only for about 60 percent of a calendar year. The
moving blades of wind machines make noise and may kill the
flying birds.
OCEAN ENERGY
Ocean water is a potential source of energy. Ocean
thermal energy and tidal energy are two important forms of ocean energy that
can be exploited for generation of electricity.
Ocean Thermal Energy : The ocean water receives
enormous amount of solar radiation.The absorbed heat raises the temperature of
surface waters. Contrary to this, the bottom waters are quite cool. There may
be a temperature difference of about 24°C between the
surface water and deep bottom waters. This
temperature difference can be exploited for hamessing the thermal energy
trapped in the ocean water.
In an Ocean Thermal Energy Conversion (OTEC) plant,
thermal energy of the ocean water is used to produce electricity. The hot
surface water is pumped into heat exchangers of the
OTEC plant to boil and pressurize liquid ammonia.
The ammonia steam is then used to drive turbines for producing electricity. The
bottom water from a depth of about 900m is pumped
to surface for cooling ammonia back into liquid
state. This liquefied ammonia is pumped back to heat exchangers to repeat the
process again. The generation of electricity from tempera-ture difference
between surface and bottom waters of ocean is known as ocean thermal
energy conversion (OTEC). A part of electricity
generated by OTEC plant is used in the plant itself for pumping cool bottom
waters to surface.
The world's first mini OTEC plant was designed and
operated near Hawaii in 1979. On basis of successful experiments, large floating OTEC plants are
technologically possible. A number
of suitable locations for OTEC plants are available
in different ocean areas, It is estimated that the ocean thermal energy
potential of the world is around 1000000 MW and that of India is
around 20000 MW, A proposal for installation of 100
MW OTEC plant costing rupees 750 crores in Tamilnadu is under consideration.
Ocean thermal energy is a tenewable and pollution
free source of energy. It requires no land area for
installation of OTEC plants. But the construc-tion, operation and maintenance
costs of OTEC plants could be too high. The sea water is
highly corrosive and can damage the metallic parts
of a plant. Large scale encroachment of sea water can also interfere and distutb
the life of marine biota. Also, the efficiency of OTEC plant is supposed to be
quite low and may require advanced technologies.
Tidal Energy : The altemate rise and fall of ocean
water due to gravitational pull of the moon and the sun is known as tide. It
happens twice a day. As a result of tides, large volume
of water flows in and out of inland bays, estuaries
and other water bodies near the coastal atea. The tidal energy associated with
the rising and falling water can be used for generating
electricity. It is possible by constructing a tidal
dam across the narrow mouth of a bay. At high
tide when the water level rises, the flood gates of
the dam are opened and water flows into the bayside reservoir. Then the gates
are closed. At low tide, the stored water is allowed to
flow back out to ocean water. This out flowing water
tums the turbines and generates elec-tricity. The La Rance Power Station
constructed across the Rance River in France is the
world's largest tidal power plant. This dam receives
water from tides upto 13.5m high. The experimental tidal power plant
constructed at the Bay of Fundy in Canada has a water level difference of 16m
between high and low tides. In India, the model tests to harness tidal
energy ate being tried. The Gulf of Kutch and the
Gulf of Cambay in Gujarat and the Sunderbans in West Bengal have been
identified as potential sites for hamessing tidal energy.
Under anaerobic conditions, the bacteria breakdown
the undigested plant material of cattle dung into biogas. The remaining solid
material is used as fertilizer for crops. Biogas can also be collected from
household wastes and industrial wastes, dumped and buried in the landfills.
Liquid fuels such as
methanol and ethanol can be prepared from biomass
and may be used in engines. Some plants like Jatropha, belonging to the family
Euphorbiaceae yield useful oil which can be used as fuel in diesel
engines.
As mentioned in the previous chapter, about half of
the world population depends upon biom-ass as a primary source of energy. It
acts as an inexhaustible energy source if managed in a sustain-able manner. In
rural India, biomass is the most important source of energy. There are more
than
1,852 million biogas plants in India and potential
exists for millions more, Cultivation of oil yielding plants is also gaining a
momentum. There is a pressure on forest sources duc to increased demand of
firewood, Undoubtedly, the use of biomass decreases our dependence on fossil
fuels, but it also contributes to the problem of global warming by increasing
the level of carbon dioxide in the atmo-
sphere. This problem can be minimized if biomass
used is replaced by biomass regenerated. As in case of wood, other forms of
biomass like animal waste and crop residues also release oxides of
sulphur and nitrogen into the atmosphere. On burning
biomass, a lot of suspended particulate matter is produced. Cutting of trees
for firewood also leads to soil erosion and desertification, When biom-ass is
bumt in traditional ‘chullahs’ or open fires, a large amount (80-90 percent) of
energy is dissi-pated into the environment.
SOLAR ENERGY
Solar radiation falling on the earth's surface is
most important renewable source of en-ergy. Every year, the earth receives
solar radiation equivalent to 1500 times the commercial energy consumption of
the world. But the problem is that unlike fossil fuels and nuclear en-ergy,
solar energy is not concentrated in localized areas. It is dispersed over the
vast surface
of the earth. In order to harness this energy, the solar
radiation is concenterated or trapped in a small area. This can be achieved
through passive solar heating or active solar heating. Pas-sive solar heating
is used to warm buildings. It makes the use of green house effect and is the
simplest, cheapest, pollution and maintenance free
method for hamessing solar energy. Some radiation trapping structural features
are incorporated in design of the buildings. These in-
clude large sun facing glass windows for receiving
more solar radiation, a few or no north facing windows, walls and floors of
concrete or stone and insulated curtains to reduce loss of
heat during night. Passive solar heating can also be
done by adding a small green house to the building. Similarly, in a solar
cooker, the trapped heat energy is used for cooking food. The glass top and
reflector of the solar cooker concentrate solar radiation inside the box. In
order to absorb more energy, the inside of cooker is blackened and the cooking
vessel is placed on a metal sheet.
Active solar heating is used to heat water. It
involves the use of specially designed collection devices to concentrate solar
energy (fig. 13.2). A typical collection device consists of a coil of
cop-capacity of the reservoir. Small scale hydroelectric plants cause little
disturbances in their natural
surroundings and are more environment friendly than
the large scale hydroelectric power plants.
GEOTHERMAL ENERGY
The interior core of the earth is extremely hot. It
contains molten rocks in the form of magma.At certain places, this magma comes
to lie below the earth's upper crust and heats the subsurface rocks. The heat
energy present in these rocks is known as geothermal energy. When the under-
ground water comes in contact with these hot rocks,
it starts boiling. Depending upon the tempera-ture of rocks, underground water
may get changed into dry steam, wet steam or hot water. The
areas in which such reserves of geothermal energy
exist are known geothermal regions. In some places, this hot water and steam
gush out in the form of hot springs and geysers.
After locating a geothermal area, a bore is drilled to obtain underground deposit of steam or hot water. These sources of geothermal energy can be used for producing electricity. The deposits of dry stream are very rare. It contains no droplets of water and can be directly used to drive turbines for generating electricity (fig. 13.5). Wet steam is super heated water under high pressure. It is a mixture
of steam and water droplets.
In order to produce electricity from wet steam, it is first spun at high speed
in a steam separator. The separated steam is then used to turn turbines.
Deposits of hot water
are more common than dry and wet steam deposits. Hot
water is used to warm residential buildings,farm buildings and to dry crops.
Electricity can also be generated from hot water. In a heat ex-
changer, the heat energy of hot water is used to
evaporate and pressurize a hydrocarbon fluid. The pressurized gaseous state of
the fluid is then used to drive turbines for generating electricity. The
scientific works in USA and UK have tested the technological possibility of
harnessing geothennal
energy from very deeply located hot dry rocks. They
drilled test wells and pumped water into these wells. The heat of the rocks
changed this water into steam that was collected back for driving turbines.
Geothermal energy accounts for 1.6. percent of the total energy consumed in the
world.
Currently, about 22 countries are hamessing energy
from their geothermal sources. More than 380 geothermal plants are being
operated in these countries. In this concern, the leading countries are Italy,
Iceland, Mexico, Japan, Indonesia, the Philppines and the United States of
America. Though in India too, about 340 hot springs have been located, yet this
energy could not be tapped on a large scale. A small project has been set up in
Manikaran in Himachal Pradesh. Another 1 KW experi-mental generator is being
operated on geothermal energy in the Puga valley in Ladakh region of
Jammu and Kashmir. This valley is situated at an
altitude of 4500m above sea level and the climate is very cold, especially
during the winter season. The people use geothermal energy for space heat-ing,
poultry farming, mushroom cultivation and wool processing. The hot geysers in
Madhya Pradesh are also being investigated for commercial hamessing of this
energy. Geothermal energy does not
depend upon weather conditions. Deposits of
geothermal energy can supply energy to the adjoining areas on a moderate cost.
It does not result in emission of carbon dioxide but it releases ammonia,
hydrogen sulphide and radioactive elements as
pollutants in air. The surrounding land may subside due to excessive removal of
underground water. Geothermal energy is not available everywhere.
NUCLEAR ENERGY
The energy released during nuclear fission or fusion is known as nuclear energy. Nuclear fission involves splitting of a heavy atom (nucleus) into two smaller atoms (nuclei) with release of large amount of energy (Fig. 13.6). In this process, the large nuclei of a heavy element like Uranium- 235 or Plutonium - 239 are bombarded with neutrons.
Addition of a neutron into the nucleus of a heavy
atom makes it quite unstable, This unstable atom (nucleus) immediately breaks
into two smaller atoms (nuclei) and 2 or 3 neutrons are also ejected
out. These neutrons then bombard the other atoms of
the heavy element and trigger a chain reaction.A large amount of heat energy is
generated at each step in this chain reaction. In nuclear fusion, two
light-weight atomic nuclei join together to form a heavier atomic nucleus. For
example, fusion of a
deuterium atom (nucleus) with a tritium atom
(nucleus) forms a helium atom (nucleus). This process is feasible at a very
high temperature and produces tremendous amount of heat. On the basis of technological
feasibility, nuclear fission reactors are used for hamessing nuclear energy. In
this reac-tor, chain reaction is performed under controlled conditions. A
typical muclear reactor consists of four main patts namely, the reactor core,
the steam generator, the turbine and the condenser (fig 13.7).
Fission of uranium fuel takes place inside the
reactor core. The pellets of uranium dioxide are loaded in the fuel rods. The
rate of chain reaction is controlled by using control rods made of special alloy.These
can absorb the free neutrons produced during fission. The heat produced by
fission is trans-
ferred to the steam generator by a primary water
circuit. Water is heated in the reactor core to about 293°C. Under high
pressure, it remains liquid and is circulated between reactor core and steam
generator. The steam is produced from a secondary water circuit in the steam
generator. It is then
used to turn turbines for generating electricity. In
the condenser, the waste steam is cooled back into liquid by a tertiary water
circuit. The same process take place in the nuclear submarines and ships.The
propelling force is obtained from the steam generated during nuclear fission
taking place inside the nuclear reactors of these submarines and ships.
The first nuclear power plant was constructed in
1957 in the United Kingdom. By 1986, there were 374 commercial nuclear reactors
in 26 countries, providing 15 percent of the world's electric-ity, The leading
countries are the United States of America, Japan, France, United Kingdom,
former Soviet Union and West Germany. The Chernobyl nuclear disaster of 1986
raised several serious concerns over the safety of nuclear plants and disposal
of the radioactive wastes. Since then, a
of these atomic power plants is about 2005 MW. It
accounts for only 3 percent of the total electric-ity produced in India.
Uranium ores are found in Jharkhand, Andhra Pradesh, Rajasthan and the
Himalayan region, These ores are processed into uranium fuel at Nuclear Fuel
complex in Andhra Pradesh, The heavy water used as a coolant in nuclear
reactors is produced in heavy water plants at Kota (Rajasthan), Baroda
(Gujarat), Tuticorin (Kerala), Thal (Maharashtra) and Talcher (Orissa).
Unlike fossil fuels, nuclear reactors do not emit
air pollutants such as carbon dioxide, oxides of sulphur, oxides of nitrogen
and particulate matter, Nuclear energy is a highly concentrated source of
energy, A small pellet of uranium dioxide contains energy equivalent of one ton
of coal. Although, the
chances of a nuclear accident are very low, but its
consequences are very dangerous. The nuclear power plants produce radioactive
waste that is extremely dangerous to human health and environ-ment. It may
cause inheritable genetic disorders. The appropriate methods for storage and
safe disposal of this waste have not been fully developed so far. The total
cost involved in construction,maintenance, operation, safety, measures, storage
and disposal of radioactive waste and dismantling
of an old reactor is considered to be very high.
NEED TO PROMOTE NON-CONVENTIONAL
SOURCES OF ENERGY
Coal, oil, natural gas and firewood are our major
conventional sources of energy. We have been exploiting these sources since
long back. Firewood has been a major source of energy since
early human settlements till the middle of
nineteenth century. Then with the advent of rapid industial-ization, coal
became the major source of energy by end of nineteenth century. Oil and natural
gas emerged as other major sources by 1930s, The long term use of these fossil
fuels has resulted in serious environmental pollution. The quality of commons
Le., air, water and soil has deteriorated to a considerable extent. This has
led to deleterious effects on human beings and other animals. More-
over, the reserves of these fossil fuels are not
unlimited, These sources are non-renewable in nature.It has taken millions of
years to forms fossil fuels in nature. If the current rate of consumption of
these fossil fuels continues, they may not last much longer in the future. In
comparison with fossil fuels, the non-conventional sources of energy cause less
pollution of the environment. Most of these sources
such as solar energy, wind energy, ocean thermal
energy, tidal energy, biomass energy and hydel energy are renewable in nature.
These are used by man and replenished by nature. The nuclear
energy has a great potential if all necessary safety
measures are developed and incorporated in the future nuclear energy plans. The
global demand of energy is increasing cach passing day. In this concem, the
non-conventional sources of energy are very promising alternative source of
energy.
Accordingly, there is an urgent need to promote
non-conventional sources of energy.
EXERCISE
{A) Very short answer type questions (1
mark each) :
1. Name different non-conventional sources of
energy.
2. Why are non-conventional sources also known as
renewable sources?
3. How can firewood be changed into charcoal?
4, Name two liquid fuels that can be produced from
biomass.
5. Give the composition of biogas.
6, Name an oil yielding plant.
7. Which one is the most important renewable source
of energy?
8. What is a solar panel?
9. What is a wind turbine?
10. What is the ideal wind speed to run a wind
turbine?
11. Define a tide?
12, Why are small scale hydroelectric plants
considered more environment friendly?
13. Name any two localities where small projects for
harnessing geothermal energy have been installed?
(B) Short answer type questions (2
marks each) :
1. Whatare the advantages of non-conventional energy
sources over the conventional sources?
2, Whatis included in biomass energy?
3, How does a photovoltaic cell produce electricity?
4. What are advantages of solar energy?
5. Whatis the limitation of solar energy?
6. Whatis a wind farm?
7. Name four major hydroelectric power stations in
India?
8. Write two drawbacks of hydel energy?
9, Whatis nuclear fusion?
10. Why should the non-conventional sources of
energy be promoted?
(C) Short answer type questions (4
marks each):
1. How is biogas produced?
2. What are the disadvantages of biogas as a source
of energy?
3. Write a short note on active solar water heating
device.
4, Explain the structure and function of a wind
mill.
5. Give a brief account of advantages and
limitations of wind energy?
6. How does a hydroelectric power station work?
7. How are the different deposits of geothermal
energy utilized?
8. Explain nuclear fission with an example.
(D) Long answer type questions: (5
marks each):
1. Describe different methods used for generating
electricity from solar energy?
2. Discuss two important forms of ocean energy.
3. Give a detailed account of method of harnessing
hydel energy. Also make a mention of its potential, advantages and drawbacks.
4. Elaborate the structure of a nuclear reactor.
What are advantages and risks associated with nuclear energy?
