a) a condensing chamber where cold water (of

a)     
Binary cycle power plant

The
difference between this and the first two technologies is that, the water or
steam which is taken from the hot reservoir which is located underneath the
surface of the earth does not come into contact with the turbine 3. Instead
this water or steam is used to heat up a secondary liquid in a secondary pipe
and this liquid has a much lower boiling point than water (as low as 14°C) 3.
The vapor from this liquid move upwards and passes through the turbine and the
pressure of this vapor is used to rotate the turbines 3. Once the turbine is
rotated, the vapor is sent to a condensing chamber where cold water (of about
19°C) is used to cool down this vapor back to its liquid form and is collected
at the bottom of the tank and the water leaves at a temperature of about 30°C
3. This liquid flows down the outlet of the tank to the pump where it is
re-pressurized and sent back into the exchanger for re-use 3. The water which
was used in the process is sent to the cooling tower where it is cooled from 30°C
to 19°C 3. Figure 4 shows a binary cycle power plant.

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This
report primarily focuses on the feasibility of geothermal energy in India and
how it can provide significant amount of new energy to the energy system in the
next three decades which results in the reduction in carbon emissions.

1)   
Energy Background in India

India
is the third largest consumer of electricity. The total installed capacity is
333.11 GW 4 and the breakdown by source is as follows:

·        
Coal – 58.5% 7

·        
Renewables – 31.8% 7

Ø  Hydro
– 14.8% 7

Ø  Wind
– 9.9% 7

Ø  Solar
– 4.5% 7

Ø  Biomass
– 2.5% 7

·        
Nuclear – 2% 7

·        
Gas – 7.6% 7

·        
Diesel – 0.3% 7

In
2016, the coil consumption in India increased by 8.3% to 212.7 million tonnes
compared to the 1.5% in global increase, resulting in India being the third
largest consumer of oil in the world 8. Between the years of 2005 and 2015,
the consumption rate increased by 4.9% in India while for the rest of the
world, it increased by 1% 8. India is the fourth largest producer of carbon
dioxide accounting for 6.81% of the total world emissions.

In
2015, the GHG emissions due to electricity production was about 2066.01 MtCO2
9. For the next few decades, the use of coal and oil will continue to
dominate the energy sector. However emissions need to be reduced by increasing
the use of green energy/non-conventional energy sources. Currently hydro, solar
and wind contribute about 29.3% of the total installed capacity 10. 30% of
the total electricity consumption comes from residential and commercial
building sectors and 55% of this electricity consumption is due to HVAC 10. More
than 65% of electricity consumption of a commercial or industrial building is
due to air-conditioning and process cooling/heating resulting in large amount
of CO2 10. This can be reduced with the use of heating/cooling
systems that use geothermal energy. The Ministry of New & Renewable Energy
(MNRE) has proposed a policy in order to implement geothermal energy and some
of the findings have been used in this report 10.

Figure
5 shows India’s projected electricity production by 2020

2.1)           
Vision and Goal of the MNRE

According
to the Geothermal Energy Development Framework, the vision is to create a
long-term energy supply of geothermal energy in order to reduce GHG emissions
by creating a geothermal industry that is sustainable, safe, secure, socially
and environmentally friendly and at the same time help in creating new
prospects of employment 10. The goal is to reach 1000 MW (thermal) and 20 MW
(electrical) Geothermal Energy Capacity by 2022 and 10,000 MW (thermal) and
1000 MW (electrical) by 2030 by collaborating with countries such as US, Philippines,
Mexico and New Zealand 10.

2.2)           
Geothermal Energy in India

India
has great potential of becoming a leading contributor in the generation of
eco-friendly and cost effective geothermal power 1. But one of the reasons
for not building up geothermal power projects is due to high availability of
coal as well as its low cost 11. However due to increasing emissions, India
needs to start going in the direction of alternative sources and geothermal
looks to be a good way to substitute some of the coal and oil used to produce
electricity. According to the Geothermal Energy Development Framework, the growth
of geothermal energy needs deeper excavation and use of energy for the
production of electricity 10. This was held up due to the lack of machinery
and equipment needed for deep drilling 10. Only thirty one areas have been
analyzed in detail and shallow drilling of up to a maximum depth of 728m in
certain areas and less in others 10. So far bathing, swimming, balneology and
in certain cases a source for cooking have been the direct-uses of geothermal
energy in the country. The annual geothermal use for these activities has
increased from 2545 TJ in 2010 to 4152TJ in 2014 and the installed capacity is
981 MWt 10.

2.3)           
History of Geothermal Studies in India

According
to the Geothermal Energy Development Framework, the Geological Survey of India
(GSI) has performed a preliminary analysis and has showed the prospects of
developing geothermal power 10. The exploration of geothermal resources
started in 1973 and the preliminary analysis shows that India is in a low and
medium heat enthalpy region (100-180°C) 10. Around 340 hot springs have been
found is different regions of India with a surface temperature ranging between 35°C
and 98°C 10.

Currently
the geothermal resources are in its nascent stages mainly due to the abundance
of coal and its cheap price 10. However due to the increasing emissions,
India needs to implementing more renewable sources of energy apart of hydro,
wind and solar and geothermal looks to be one of those sources 10.

2.4)           
Geothermal Resources in India

There
are 2 enthalpy geothermal system in India as follows:

a)      Medium
Enthalpy (100°C-200°C)

This
region is associated with:

·        
The geothermal fields of Puga-Chumathang,
Parbati, Beas and Satluj Valley as these regions have younger intrusive
granites 10.

·        
West coast areas of Maharashtra; along the
Son-Narmada-Tapi lineament belt at Salbardi, Tapi; Satpura areas in
Maharashtra; Tattapani in Chhattisgarh and Rajgir-Monghyar in Bihar, Tatta and
Jarom in Jharkhand and Eastern Ghat tracts of Orissa 10.

·        
Rift and grabens of Gondwana basins of
Damodar, Godavari and Mahanadi Valleys 10.

·        
Quaternary and tertiary deposits found in
a graben in the Cambay basin of the West Coast 10.

b)      Low
Enthalpy (<100°C) This region is associated with: ·         Tertiary tectonism and neotectonic activity 10. ·         Shield areas with localized abnormal heat flow, which is normally very low 10. Figure 6 shows 7 geothermal provinces in India. Figure 6 – 7 Geothermal Provinces 12 India is divided into orogenic and non-orogenic geothermal regions. The orogenic regions are as follows: ·         Himalayan Region - Northwest Ø  Puga Region o   This region is about 180km from Leh in Ladakh Region of Jammu and Kashmir across the Great Himalayan range at an altitude of 4400m above mean sea level (amsl) 13. The thermal phenomenon of this region appear in the form of hot springs, hot pools, sulphur condensates, borax evaporates that have an aerial extent of 4km 13. Figure 7a) shows a hot spring geyser at Puga and Figure 7b) shows the sulphur deposits at Puga 13. The hot springs have a temperature of about 30°C to 84°C and the maximum discharge rate from a single spring is 5litres/sec 13. o   Geophysical surveys indicate that the southwest part of the Puga geothermal region has a really low resistivity zone of about 2-10 ?m indicating the occurrence of thermal-water in the sub-surface 13. o   The water in this region has a ph level between 6 and 8.3 and is mainly of NAHCO3Cl type 13. Geochemical thermometers indicate (based on the concentration of Na,K,Ca and Mg) the chance of having thermal liquids with temperatures between 220°C-260°C 13. The temperature gradient is high between 0.35 to 2.5°C/m and some places have a gradient of about 6.8°C/m 13. o   34 boreholes with depths ranging between 28.5m and 384.7m have been dug in this region 13. The boreholes that have struck steam-water have generated 10-15% steam with a temperature of 140°C 13. Wellhead measurements was taken for 8 boreholes and the total discharge for these 8 boreholes was found to be 190 tones/hour consisting of steam/water 13. The maximum discharge of a single drill hole was found to be 30 tones/hour 13.  o   Using the geothermal fluids in this region, space heating for a 5m*5m*2.5m hut was successful heated to a temperature greater than 20°C and maintained. Borax and sulphur refinement was also able to be done 13. o   Currently, this region is the only capable region of producing either primary cycle electrical power or binary power but reservoir simulation studies indicates that a power of 3 MW can be generated if deeper levels are investigated up to at least 500m 13. Ø  Chhumathang Region: o   This region is located 40km north of Puga. Magnetic, seismic refraction and resistivity assessments have been done in this regions 13. The assessment indicates that region has low resistivity of about 13-30 ?m up to a depth of 300m 13. o   The thermal manifestations appear in the form of a carbonate plateau with a diameter of about 100m and height of about 6-10m as shown in Figure 8 13.