PROJECT BASED LEARNING
Prof. JYOTSANA KAUSHAL
Dept: Applied Science
India imports nearly 22% of its total energy demand. The price variations in
the global oil and natural gas poses a great problem to our „Energy Security‟
considerably. With wide network of research and development of premier
organizations such as CSIR, DST and also the premier energy oriented
organizations such as ONGC, OIL, Reliance, NTPC Ltd, NHPC Ltd., etc are
playing a significant role in planning for the strategic energy research towards the
India is planning to have a quantum jump from a developing country to a
developed country. Its‟ energy consumption is directly linked to industrialization
and the living standards of it‟s population. Fig.1 shows the per capita consumption
of energy by different countries. Our consumption is less than 1/10th as compared
to developed counries, say Germany or Japan. The rapid economic development of
our country coupled with population growth in recent years has been driving energy
demand growth and still the gap between production and demand is becoming
wider and wider. Although India is blessed with vast potential in the form of new
and renewable natural resources, such as solar, wind, bio-mass, hydro, gas hydrates,
geothermal etc., their exploitation is not near it‟s maximum potential.
Towards this direction, the present study reviews the geothermal potential in
India along with our present day knowledge and also discusses the future
programmes and plans to develop geothermal energy.
WHAT IS GEOTHERMAL ENERGY ?
Geothermal name origins from the Greek roots geo meaning earth,
and thermos meaning heat . Geothermal energy is the earth’s natural heat available
inside the earth. This thermal energy contained in the rock and fluid that filled up
fractures and pores in the earth’s crust can profitably be used for various purposes. It
is believed that ultimate source of geothermal energy derived from the earth due to
radioactive decay occurring within the earth at deep crustal depths. 0.1% of the
energy stored in Earth’s crust could satisfy the world energy consumption for 10,000
years. At all locations, the heat reaches the surface of the earth in a defusing manner.
The earth’s heat increases with depth at a rate of 30 o C per km and this way the
centre of the earth is estimated to have about 5000 o C . However, due to geological
processes and tectonic disturbances, heat sources become relatively shallow at
certain locations. Greater the temperature higher will be its utility. For example, the
heat source of high temperature is generally used for electric power generation. As
on today, geothermal electric power generation in US is approximately above 2200
MW. This is equivalent to 4 large nuclear power plants. The low and moderate
temperature resource can be used for direct applications and also using ground
source heat pumps. Application of direct use involves heating of the buildings,
industrial processes, greenhouses, aquaculture and in holiday resorts.
Ground heat source uses the groundwater as a medium of transport that
can be used to transfer the heat from the soil down below to the surface. As on
today, the current world production of geothermal energy for both direct and indirect
uses has occupied a third place among the various renewable energy sources such as
hydroelectricity, biomass, solar power and wind power. Although its potential is
impressive from various users in different countries, its utility in India is near zero.
The success of geothermal use depends on the technical information about the
various geothermal provinces.
The oldest known pool fed by a hot spring, built in the Qin dynasty in the 3rd
Hot springs have been used for bathing at least since paleolithic times. The oldest
known spa is a stone pool on China’s Lisan mountain built in the Qin dynasty in the
3rd century BC, at the same site where the Huaqing Chi palace was later built. In
the first century AD, Romans conquered Aquae Sulis, nowBath, Somerset, England,
and used the hot springs there to feed public baths and underfloor heating. The
admission fees for these baths probably represent the first commercial use of
geothermal power. The world's oldest geothermal district heating system
in Chaudes-Aigues, France, has been operating since the 14th century. The
earliest industrial exploitation began in 1827 with the use of geyser steam to
extract boric acid from volcanic mud in Larderello, Italy.
In 1892, America's first district heating system in Boise, Idaho was powered
directly by geothermal energy, and was copied in Klamath Falls, Oregon in 1900. A
deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers
were used to heat greenhouses in Iceland and Tuscany at about the same
time. Charlie Lieb developed the first downhole heat exchanger in 1930 to heat his
house. Steam and hot water from geysers began heating homes in Iceland starting
Different Geothermal Energy Sources
Hot Water Reservoirs: As the name implies these are reservoirs of hot
underground water. There is a large amount of them in the US, but they are
more suited for space heating than for electricity production.
Natural Stem Reservoirs: In this case a hole dug into the ground can cause
steam to come to the surface. This type of resource is rare in the US.
Geopressured Reservoirs: In this type of reserve, brine completely
saturated with natural gas in stored under pressure from the weight of
overlying rock. This type of resource can be used for both heat and for
Normal Geothermal Gradient: At any place on the planet, there is a normal
temperature gradient of +300C per km dug into the earth. Therefore, if one
digs 20,000 feet the temperature will be about 1900C above the surface
temperature. This difference will be enough to produce electricity.
However, no useful and economical technology has been developed to
extracted this large source of energy.
Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to
Normal Geothermal Gradient, but the gradient is 400C/km dug underground.
Molten Magma: No technology exists to tap into the heat reserves stored
in magma. The best sources for this in the US are in Alaska and Hawaii.
Direct uses of geothermal energy
resorts and pools
Geothermal reservoirs constitute one of the important renewable sources of
energy currently being used to meet energy demands. Near the surface of the
earth various mega geological and tectonic features associated with geothermal
energy are spreading ridges, transform faults, subduction zones etc. They form a
vast network that divides our planet into distinct lithospheric units. For example,
the plate boundaries correspond to fractured zones of the earth and characterised
by large heat source that can be seen on the surface with many number of
volcanoes, frequent seismic activity etc. These typical regions can also manifest
itself on the surface such as geysers, hot springs etc. The geothermal potential
stands out with the availability of large potential . However, the technology need
to be developed to harness this energy source.
Through geological and geophysical investigations, geothermal source buried at
certain depth can be delineated for exploitation as an energy source. For example,
pacific plate boundary, all along the western coast of north and south American
continent, well-known geothermal provinces such as Imperial Valley, Cerro Prieto,
the geysers, Ahuachapan, Eltatio etc. can be observed. Similarly, the subduction
zones and along the Indian plate boundary, the geothermal reservoir systems of
Philippines, Himalayan belt regions can be seen. a summary of the countries and
installed electric power capacity..
NAME OF THE COUNTRY
INSTALLED GEOTHERMAL CAPACITY
Borehole Heat Exchange
This type uses one or two underground vertical loops that extend 150 meters
below the surface
Dry Steam Plants
These were the first type of plants created. They use underground steam to
directly turn the turbines.
Flash Steam Plants
These are the most common plants. These systems pull deep, high pressured hot
water that reaches temperatures of 3600F or more to the surface. This water is
transported to low pressure chambers, and the resulting steam drives the
turbines. The remaining water and steam are then injected back into the source
from which they were taken.
Binary Cycle Plants
This system passes moderately hot geothermal water past a liquid, usually an
organic fluid, that has a lower boiling point. The resulting steam from the organic
liquid drives the turbines. This process does not produce any emissions and the
water temperature needed for the water is lower than that needed in the Flash
Steam Plants (2500F – 3600F).
Hot Dry Rocks
The simplest models have one injection well and two production wells.
Pressurized cold water is sent down the injection well where the hot rocks heat
the water up. Then pressurized water of temperatures greater than 2000F is
brought to the surface and passed near a liquid with a lower boiling temperature,
such as an organic liquid like butane. The ensuing steam turns the turbines. Then,
the cool water is again injected to be heated. This system does not produce any
emissions. US geothermal industries are making plans to commercialize this new
GEOTHERMAL PROVINCES OF INDIA
Rocks covered on the surface of India ranging in age from more than 4500 million
years to the present day and distributed in different geographical units. The rocks
comprise of Archean, Proterozoic, the marine and continental Palaeozoic,
Mesozoic, Teritary, Quaternary etc., More than 300 hot spring locations have been
identified by Geological survey of India (Thussu, 2000). The surface temperature of
the hot springs ranges from 35 C to as much as 98 C. These hot springs have been
grouped together and termed as different geothermal provinces based on their
occurrence in specific geotectonic regions, geological and strutural regions such as
occurrence in orogenic belt regions, structural grabens, deep fault zones, active
volcanic regions etc., Different orogenic regions are – Himalayan geothermal
province, Naga-Lushai geothermal province, Andaman-Nicobar Islands geothermal
province and non-orogenic regions are – Cambay graben, Son-Narmada-Tapi
graben, west coast, Damodar valley, Mahanadi valley, Godavari valley etc., Figure
4 shows different geothermal provinces of India.
GEOTHERMAL POTENTIAL AND RESOURCES OF INDIA
From geological, geochemical, shallow geophysical and shallow drilling data it is
estimated that we have about 10000 MWe of geothermal power potential that
can be harnessed for various purposes. To exploit the geothermal energy source,
we need to map the deep subsurface structure and to demarcate the area of
geothermal heat trapped inside the surface such that decisions regarding deep
drilling, estimation of it’s potential, number of years that can profitably used etc
parameters can be estimated. This can be carried out with the help of geochemical
and deep geophysical techniques. Geological survey of India has made concerted
efforts in this direction by using shallow geophysical technique, geochemical
sampling with shallow (< km) bore hole drilling also in several geothermal fields in
India. The data base generated by GSI is a valuable document with which heat flow
map of India, geothermal atlas have been prepared (Ravishanker, 1988). NGRI has
also made concerted efforts in different geothermal regions of India (Gupta and
Roy, 2006). In order to map the deep structure of geothermal regions, more
recently (since 1995) NGRI has been using a deep geophysical technique –
magnetotellurics (MT) – to map the anomalous deep geothermal fields. The
regions covered by MT are Tatapani, Chattisgarh, Puga, J &K, Tapovan-VishnugadBadrinath in Uttarakhand, Surajkund, Jharkhand, Kullu-Manali-Manikaran in
Himachal Pradesh etc., (Harinarayana et al 2000,2003,2004 and 2005). These
studies have provided valuable information and have identified the locations for
deep drilling for possible use of geothermal energy for power generation. The
estimated temperatures of these geothermal fields based on shallow drilling and
deep geophysical studies are shown
Puga geothermal field
240 C at 2000m
From geochemical and deep
geophysical studies (MT)
120 oC - 150 oC at500
meter and 200 Cat 2000 m
Magnetotelluric survey done by
100 oC at 430 meter
Magnetotelluric survey done by
160 oC at 1900meter
Steam discharge was estimated
3000 cu meter/ day with high
150 oC estimated
Magneto-telluric study was
done by NGRI
Deep drilling required to
ascertain geothermal field
Magneto-telluric study was
done by NGRI.
Heat rate 128.6 mW/m2
Kullu (H P)
Magneto-telluric study was
done by NGRI
Heat flow rate 130 mW/m2
Kullu (H P)
Magneto-telluric study was
done by NGRI
Advantages of Geothermal Energy
When a power station harnesses geothermal power in the correct manner, there are
no by products, which are harmful to the environment. Environmentalists should be
happy about that! There is also no consumption of any type of fossil fuels. In
addition, geothermal energy does not output any type of greenhouse effect. After
the construction of a geothermal power plant, there is little maintenance to contend
with. In terms of energy consumption, a geothermal power plant is self-sufficient.
Another advantage to geothermal energy is that the power plants do not have to be
huge which is great for protecting the natural environment.
Useful minerals, such as zinc and silica, can be extracted from underground
Geothermal energy is “homegrown.” This will create jobs, a better global
trading position and less reliance on oil producing countries.
US geothermal companies have signed $6 billion worth of contracts to build
plants in foreign countries in the past couple of years.
In large plants the cost is 4-8 cents per kilowatt hour. This cost is almost
competitive with conventional energy sources.
Geothermal plants can be online 100%-90% of the time. Coal plants can
only be online 75% of the time and nuclear plants can only be online 65% of
Flash and Dry Steam Power Plants emit 1000x to 2000x less carbon dioxide
than fossil fuel plants, no nitrogen oxides and little SO2.
Geothermal electric plants production in 13.380 g of Carbon dioxide per
kWh, whereas the CO2 emissions are 453 g/kWh for natural gas, 906g g/kWh
for oil and 1042 g/kWh for coal.
Binary and Hot Dry Rock plants have no gaseous emission at all.
Geothermal plants do not require a lot of land, 400m2 can produce a gigawatt
of energy over 30 years.
Geothermal Heat Pumps:
- produces 4 times the energy that they consume.
-initially costs more to install, but its maintenance cost is 1/3 of the
cost for a typical conventional heating system and it decreases
electric bill. This means that geothermal space heating will save the
-can be installed with the help of special programs that offer low
interest rate loans.
Disadvantages of Geothermal Energy
There are several disadvantages to geothermal energy. First, you cannot just build a
geothermal power plant in some vacant land plot somewhere. The area where a
geothermal energy power plant would be built should consist of those suitable hot
rocks at just the right depth for drilling. In addition, the type of rock must be easy to
drill into. It is important to take care of a geothermal site because if the holes were
drilled improperly, then potentially harmful minerals and gas could escape from
under ground. These hazardous materials are nearly impossible to get rid of
properly. Pollution may occur due to improper drilling at geothermal stations.
Unbelievably, it is also possible for a specific geothermal area to run dry or lose
Brine can salinate soil if the water is not injected back into the reserve after
the heat is extracted.
Extracting large amounts of water can cause land subsidence, and this can
lead to an increase in seismic activity. To prevented this the cooled water
must be injected back into the reserve in order to keep the water pressure
Power plants that do not inject the cooled water back into the ground can
release H2S, the “rotten eggs” gas. This gas can cause problems if large
quantities escape because inhaling too much is fatal.
One well “blew its top” 10 years after it was built, and this threw hundreds
of tons of rock, mud and steam into the atmosphere.
There is the fear of noise pollution during the drilling of wells.
To make sure we have plenty of energy in the
future, it's up to all of us to use energy wisely.
Imagination is more
We must all conserve energy and use it
efficiently. It's also up to those who will create
the new energy technologies of the future.
knowledge, for knowledge
is limited, whereas
imagination embraces the
All energy sources have an impact on the
entire world - stimulating
environment. Concerns about the greenhouse
progress, giving birth to
effect and global warming, air pollution, and
energy security have led to increasing interest
and more development in renewable energy
sources such as solar, wind, geothermal, wave
- Albert Einstein
power and hydrogen.
But we'll need to continue to use fossil fuels
and nuclear energy until new, cleaner
technologies can replace them. One of you
who is reading this might be another Albert
Einstein or Marie Curie and find a new source
of energy. Until then, it's up to all of us.
The future is ours, but we need energy to get