Do you know what renewable
sources of energy are and why we
should think of these alternative
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
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 can 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
a. domestic lighting
b. street lighting
c. village electrification
d. water pumping
e. desalination of salty water
f. powering of remote telecommunication repeater
g. railway signals.
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
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
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.
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.
Large amounts of solar energy is stored in the oceans and
seas. 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.
The utilization of geothermal energy (in Greek it means
heat from the earth) 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
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.
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
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.
What are fuel cells? Fuel cells are electrochemical
devices that convert the chemical energy of a fuel
directly and very efficiently into electricity (DC) and heat,
thus doing away with combustion. The most suitable fuel
for such cells is hydrogen or a mixture of compounds
containing hydrogen. A fuel cell consists of an electrolyte
sandwiched between two electrodes. Oxygen passes
over one electrode and hydrogen over the other, and
they react electrochemically to generate electricity,
water, and heat.
Fuel cells can supply combined heat and power to
commercial buildings, hospitals, airports and military
installation at remote locations. Fuel cells have efficiency
levels up to 55% as compared to 35% of conventional
power plants. The emissions are significantly lower (CO2
and water vapour being the only emissions). Fuel cell
systems are modular (i.e. additional capacity can be
added whenever required with relative ease) and can be
set up wherever power is required.
Co-generation is the concept of producing two forms of
energy from one fuel. One of the forms of energy must
always be heat and the other may be electricity or
mechanical energy. In a conventional power plant, fuel is
burnt in a boiler to generate high-pressure steam. This
steam is used to drive a turbine, which in turn drives an
alternator through a steam turbine to produce electric
power. The exhaust steam is generally condensed to water
which goes back to the boiler.
As the low-pressure steam has a large quantum of heat
which is lost in the process of condensing, the efficiency of
conventional power plants is only around 35%. In a
cogeneration plant, very high efficiency levels, in the range
of 75%–90%, can be reached. This is so, because the low-
pressure exhaust steam coming out of the turbine is not
condensed, but used for heating purposes in factories or
Since co-generation can meet both power and heat needs,
it has other advantages as well in the form of significant
cost savings for the plant and reduction in emissions of
pollutants due to reduced fuel consumption.
In 1975, when Anna Hazare, a retired army man, went back to his village in
Ahmednagar district, Maharashtra, he found the village reeling under drought, poverty,
debt, and unemployment. He decided to mobilize the people and, with the collective
support of all the villagers, he began to introduce changes.
Today Ralegaon Siddhi is being taken as a role model for other villages by the
Maharashtra government and by other states too. Massive tree plantation has been
undertaken, and hills have been terraced to check erosion. Large canals with ridges on
either side have been dug to retain rainwater. As a result, the water table in this area is
now considerably higher and the wells and tube wells are never dry, making it possible
to raise three crops a year where only one was possible before.
The village's biggest achievement is undoubtedly in the area of non-conventional
energy. All the streets in the village are lit by solar lights, each with a separate panel.
There are four large community biogas plants and one of them is fitted to the
community toilet. There is a large windmill used for pumping water. A number of
households have their own biogas plants. The village is self sufficient .
Ralegaon Siddhi, a success story –