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Renewable
Energy
In the past century, it has been seen that the consumption of
non-renewable sources of energy has caused more environmental
damage than any other human activity. Electricity generated
from fossil fuels such as coal and crude oil has led to high
concentrations of harmful gases in the atmosphere. This has
in turn led to many problems being faced today such as ozone
depletion and global warming. Vehicular pollution has also been
a major problem.
Therefore, alternative sources of energy have become very important
and relevant to today’s world. These sources, such as
the sun and wind, can never be exhausted and therefore are called
renewable. They cause less emissions and are available locally.
Their use can, to a large extent, reduce chemical, radioactive,
and thermal pollution. They stand out as a viable source of
clean and limitless energy. These are also known as non-conventional
sources of energy. Most of the renewable sources of energy are
fairly non-polluting and considered clean though biomass, a
renewable source, is a major polluter indoors.
Under the category of renewable energy or non-conventional energy
are such sources as the sun, wind, water, agricultural residue,
firewood, and animal dung. The non-renewable sources are the
fossil fuels such as coal, crude oil, and natural gas. Energy
generated from the sun is known as solar energy. Hydel is the
energy derived from water. Biomass –firewood, animal dung,
biodegradable waste from cities and crop residues- is a source
of energy when it is burnt. Geothermal energy is derived from
hot dry rocks, magma, hot water springs, natural geysers, etc.
Ocean thermal is energy derived from waves and also from tidal
waves.
Through the method of co-generation a cleaner and less polluting
form of energy is being generated. Fuel cells are also being
used as cleaner energy source. In India a number of initiatives
have been taken. A good example is the model village of Ralegaon
Siddhi.
When you burn a piece of wood it turns into ash. Can you use
this ash to again light a fire? No, You cannot do this. This
is exactly what happens to the non renewable sources of energy
such as coal, natural gas and oil. Once you burn them they cannot
be reused. Other than this it also causes extensive damage to
the environment.
Solar
Energy
Solar energy is the most readily available source of energy.
It does not belong to anybody and is, therefore, free. It is
also the most important of the non-conventional sources of energy
because it is non-polluting and, therefore, helps in lessening
the greenhouse effect.
Solar energy has been used since prehistoric times, but in a
most primitive manner. Before 1970, some research and development
was carried out in a few countries to exploit solar energy more
efficiently, but most of this work remained mainly academic.
After the dramatic rise in oil prices in the 1970s, several
countries began to formulate extensive research and development
programmes to exploit solar energy.
When we hang out our clothes to dry in the sun, we use the energy
of the sun. In the same way, solar panels absorb the energy
of the sun to provide heat for cooking and for heating water.
Such systems are available in the market and are being used
in homes and factories.
In the next few years it is expected that millions of households
in the world will be using solar energy as the trends in USA
and Japan show. In India too, the Indian Renewable Energy Development
Agency and the Ministry of Non-Conventional Energy Sources are
formulating a programme to have solar energy in more than a
million households in the next few years. However, the people’s
initiative is essential if the programme is to be successful.
India is one of the few countries with long days and plenty
of sunshine, especially in the Thar desert region. This zone,
having abundant solar energy available, is suitable for harnessing
solar energy for a number of applications. In areas with similar
intensity of solar radiation, solar energy could be easily harnessed.
Solar thermal energy is being used in India for heating water
for both industrial and domestic purposes. A 140 MW integrated
solar power plant is to be set up in Jodhpur but the initial
expense incurred is still very high. Solar energy can also be
used to meet our electricity requirements. Through Solar Photovoltaic
(SPV) cells, solar radiation gets converted into DC electricity
directly. This electricity can either be used as it is or can
be stored in the battery. This stored electrical energy then
can be used at night. SPV can be used for a number of applications
such as:
- Domestic lighting
- Street lighting
- Village electrification
- Water pumping
- Desalination of salty water
- Powering of remote telecommunication repeater stations
- Railway signals.
If the means to make efficient use of solar energy could
be found, it would reduce our dependence on non-renewable
sources of energy and make our environment cleaner.
India receives solar energy equivalent
to over 5000 trillion kWh/year, which is far more than the
total energy consumption of the country.
Wind energy
Wind energy is the kinetic energy associated with the movement
of atmospheric air. It has been used for hundreds of years
for sailing, grinding grain, and for irrigation. Wind energy
systems convert this kinetic energy to more useful forms of
power. Wind energy systems for irrigation and milling have
been in use since ancient times and since the beginning of
the 20th century it is being used to generate electric power.
Windmills for water pumping have been installed in many countries
particularly in the rural areas.
Wind turbines transform the energy in the wind into mechanical
power, which can then be used directly for grinding etc. or
further converting to electric power to generate electricity.
Wind turbines can be used singly or in clusters called ‘wind
farms’. Small wind turbines called aero-generators can
be used to charge large batteries.
Five nations – Germany, USA, Denmark, Spain and India
– account for 80% of the world’s installed wind
energy capacity. Wind energy continues to be the fastest growing
renewable energy source with worldwide wind power installed
capacity reaching 14,000 MW.
Realizing the growing importance of wind energy, manufacturers
have steadily been increasing the unit size of the wind electric
generators since the late 1980s. Another important development
has been the offshore (i.e. in the sea) wind farms in some
regions of Europe, which have several advantages over the
on-shore ones. The third major development has been the use
of new techniques to assess the wind resource for techno-commercial
viability. In India the states of Tamilnadu and Gujarat lead
in the field of wind energy. At the end of March 2000 India
had 1080-MWs capacity wind farms, of which Tamilnadu contributed
770-MW capacity. Gujarat has 167MW followed by Andhra Pradesh,
which has 88 MW installed wind farms.There are about a dozen
wind pumps of various designs providing water for agriculture,
afforestation, and domestic purposes, all scattered over the
country.
The design of the Auroville multi-blade windmill has evolved
from the practical experience gained in operating these mills
over a period of 20 years or so. It has a high tripod tower
and its double-action pump increases water output by about
60% compared to the conventional single-action pumps.
India ranks 5th in the world with a
total wind power capacity if 1080MW out of which 1025Mw haev
been established in commercial projects
Hydel energy
Energy from water sources
The energy in the flowing water can be used to produce electricity.
Waves result from the interaction of the wind with the surface
of the sea and represent a transfer of energy from the wind
to the sea. Energy can be extracted from tides by creating
a reservoir or basin behind a barrage and then passing tidal
waters through turbines in the barrage to generate electricity.
Mini or Micro Hydro power
Hydro power is one of the best, cheapest, and cleanest source
of energy, although, with big dams, there are many environmental
and social problems as has been seen in the case of the Tehri
and the Narmada Projects. Small dams are, however, free from
these problems. This is in fact one of the earliest known
renewable energy sources, in the country (since the beginning
of the 20th century).
In fact, for the last few hundred years, people living in
the hills of the Himalayas have been using water mills, or
chakki, to grind wheat. The 130 KW small hydropower plant
in Darjeeling set up in 1897, was the first in India. Besides
being free from the problem of pollution, such plants are
also free from issues and controversies that are associated
with the bigger projects, namely affecting the lives of thousands
of people living along the banks of the rivers, destruction
of large areas under forest, and seismological threats.
New environmental laws affected by the danger of global warming
have made energy from small hydropower plants more relevant.
These small hydropower plants can serve the energy needs of
remote rural areas independently. The real challenge in a
remote area lies in successful marketing of the energy and
recovering the dues. Local industries should be encouraged
to use this electricity for sustainable development.
It is a technology with enormous potential, which could exploit
the water resources to supply energy to remote rural areas
with little access to conventional energy sources. It also
eliminates most of the negative environmental effects associated
with large hydro projects.
Energy from the sea - Ocean thermal,
tidal and wave energy
Large amounts of solar energy is stored in the oceans and
seas. On an average, the 60 million square kilometre of the
tropical seas absorb solar radiation equivalent to the heat
content of 245 billion barrels of oil. Scientists feel that
if this energy can be tapped a large source of energy will
be available to the tropical countries and to other countries
as well. The process of harnessing this energy is called OTEC
(ocean thermal energy conversion). It uses the temperature
differences between the surface of the ocean and the depths
of about 1000m to operate a heat engine, which produces electric
power. Energy is also obtained from waves and tides. The first
wave energy, project with a capacity of 150MW, has been set
up at Vizhinjam near Trivandrum. A major tidal wave power
project costing of Rs.5000 crores, is proposed to be set up
in the Hanthal Creek in the Gulf of Kutch in Gujarat.
In some countries such as Japan small scale power generators
run by energy from waves or the ocean, have been used as power
sources for channel marking buoys.
On an average, the 60 million sq km
of tropical seas absorb solar radiation equal to the heat
content of 245 billion barrels of oil.
Geothermal energy
We live between two great sources of energy, the hot rocks
beneath the surface of the earth and the sun in the sky. Our
ancestors knew the value of geothermal energy; they bathed
and cooked in hot springs. Today we have recognized that this
resource has potential for much broader application.
The core of the earth is very hot and it is possible to make
use of this geothermal energy (in Greek it means heat from
the earth). These are areas where there are volcanoes, hot
springs, and geysers, and methane under the water in the oceans
and seas. In some countries, such as in the USA water is pumped
from underground hot water deposits and used to heat people’s
houses.
The utilization of geothermal energy for the production of
electricity dates back to the early part of the twentieth
century. For 50 years the generation of electricity from geothermal
energy was confined to Italy and interest in this technology
was slow to spread elsewhere. In 1943 the use of geothermal
hot water was pioneered in Iceland. In India, Northwestern
Himalayas and the western coast are considered geothermal
areas. The Geological Survey of India has already identified
more than 350 hot spring sites, which can be explored as areas
to tap geothermal energy. Satellites like the IRS-1 have played
an important role, through infrared photographs of the ground,
in locating geothermal areas. The Puga valley in the Ladakh
region has the most promising geothermal field. An experimental
1-kW generator is already in operation in this area. It is
being used mainly for poultry farming, mushroom cultivation,
and pashmina-wool processing, all of which need higher temperature.
Geothermal manifestations are wide spread
in India in the form of 340 hot spring sites.
Biomass
Biomass is a renewable energy resource derived from the carbonaceous
waste of various human and natural activities. It is derived
from numerous sources, including the by-products from the
timber industry, agricultural crops, raw material from the
forest, major parts of household waste and wood.
Biomass does not add carbon dioxide to the atmosphere as it
absorbs the same amount of carbon in growing as it releases
when consumed as a fuel. Its advantage is that it can be used
to generate electricity with the same equipment or power plants
that are now burning fossil fuels. Biomass is an important
source of energy and the most important fuel worldwide after
coal, oil and natural gas.
Traditional use of biomass is more than its use in modern
application. In the developed world biomass is again becoming
important for applications such as combined heat and power
generation. In addition, biomass energy is gaining significance
as a source of clean heat for domestic heating and community
heating applications. In fact in countries like Finland, USA
and Sweden the per capita biomass energy used is higher than
it is in India, China or in Asia.
Biomass fuels used in India account for about one third of
the total fuel used in the country, being the most important
fuel used in over 90% of the rural households and about 15%
of the urban households.
Instead of burning the loose biomass fuel directly, it is
more practical to compress it into briquettes (compressing
them through a process to form blocks of different shapes)
and thereby improve its utility and convenience of use. Such
biomass in the dense briquetted form can either be used directly
as fuel instead of coal in the traditional chulhas and furnaces
or in the gasifier. Gasifier converts solid fuel into a more
convenient-to-use gaseous form of fuel called producer gas.
Scientists are trying to explore the advantages of biomass
energy as an alternative energy source as it is renewable
and free from net CO2 (carbon dioxide) emissions, and is abundantly
available on earth in the form of agricultural residue, city
garbage, cattle dung, firewood, etc. Bio-energy, in the form
of biogas, which is derived from biomass, is expected to become
one of the key energy resources for global sustainable development.
At present, biogas technology provides an alternative source
of energy in rural India for cooking. It is particularly useful
for village households that have their own cattle. Through
a simple process cattle dung is used to produce a gas, which
serves as fuel for cooking. The residual dung is used as manure.
Biogas plants have been set up in many areas and are becoming
very popular. Using local resources, namely cattle waste and
other organic wastes, energy and manure are derived. A mini
biogas digester has recently been designed and developed,
and is being in-field tested for domestic lighting.
Indian sugar mills are rapidly turning to bagasse, the leftover
of cane after it is crushed and its juice extracted, to generate
electricity. This is mainly being done to clean up the environment,
cut down power costs and earn additional revenue. According
to current estimates, about 3500 MW of power can be generated
from bagasse in the existing 430 sugar mills in the country.
Around 270 MW of power has already been commissioned and more
is under construction.
Half a kilo of dry plant tissue can
produce as much as 1890 KCal of heat which is equivalent to
the heat available from a quarter of kilogram of coal.
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