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Renew | January 2016

Warming up to the Idea

Besides being a zero carbon emitting source of energy, costs of geothermal has significantly reduced over the years, making it an available option for India. One that the Indian government too is contemplating.

Energy is essential for everyday functioning. Currently, majority of our energy needs are met by conventional sources of energy. But, if we need to sustain the world we live in, developing and investing in renewable sources would be the way to go. Taking a cue, the Government of India (GoI) unveiled new renewable targets for 2022 (100 GW solar, 60 GW wind and 15 GW from biomass, geothermal, hydel etc.). According to data provided by Energy Alternatives India (EAI), geothermal power plants operated in at least 24 countries in 2010, and geothermal energy was used directly for heat in at least 78 countries. These countries currently have geothermal power plants with a total capacity of 10.7 GW, but 88 per cent of it is generated in just seven countries: the United States, the Philippines, Indonesia, Mexico, Italy, New Zealand, and Iceland.

The most significant capacity increases since 2004 were seen in Iceland and Turkey. Both countries doubled their capacity. Iceland has the largest share of geothermal power contributing to electricity supply (25 per cent), followed by the Philippines (18 per cent).

What is geothermal energy?
Geothermal energy is a clean and sustainable alternative source of energy. Made of two Greek words  geo which means ´earth´, and therme, which means ´heat´, geothermal literally means heat from the earth. Resources of geothermal energy range from the moderate-to-low temperature hot spring systems to hot rock found a few miles beneath the earth´s surface, and down even deeper to the extremely high temperatures of molten rocks.

Geological, geophysical and hydrological processes in favourable environments form a geothermal system. The underground circulating water in aquifers acquires heat from the earth´s thermal gradient of around 30¦C/km. At places, geothermal gradient is more than the normal due to some geological conditions. The heat is transferred from the interior of the earth to the circulating water by conduction and convection.

Geothermal energy can be located at various depths but the economically recoverable energy is confined to depths of 3-4 km. The recoverable heat energy is possible only from circulating hydrothermal fluids. Geothermal resources account for only a small part of the world´s present day energy consumption. The geothermal resources can be classified into three categories, viz hydrothermal, geopressure and hot dry rocks.

Geothermal in India
In India, exploration and study of geothermal fields started in 1970. The GSI (Geological Survey of India) has identified 350 geothermal energy locations in the country. The most promising of these is in Puga valley of Ladakh. The estimated potential for geothermal energy in India is about 10,000 MW.

The Ministry of Power and Irrigation constituted a committee on ´Hot Springs´ in the year 1963, to explore the commercial utilisation potential of thermal springs in India.

The committee inducted members from the GSI, NGRI and Jadavpur University, Kolkata. All the thermal springs of India were classified on the basis of their geo-tectonic setup and grouped into six Geothermal Provinces as follows:
  • I - Himalayan province - Tertiary orogenic belt with tertiary magmatism
  • II - Areas of faulted blocks - Aravalli belt, Naga-Lushi, west coast regions and Son-Narmada lineament - aka Son-Narmada-Tapi (SONATA)
  • III - Volcanic arc - Andaman and Nicobar arc
  • IV - Deep sedimentary basin of tertiary age such as Cambay basin in Gujarat
  • V - Radioactive province - Surajkund, Hazaribagh, Jharkhand
  • VI - Cratonic province - peninsular India

Ongoing Projects in India include the magneto-telluric investigations in Tattapani geothermal area in Madhya Pradesh and magneto-telluric investigations in Puga geothermal area in Ladakh region, Jammu & Kashmir.

Advantages
The geothermal power plants have almost zero emission, with great potential as a clean, green and naturally occurring renewable source of energy. Geothermal hot water can be used for many applications that require heat including heating buildings, raising plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes. It can be used for generating electricity as well. Geothermal has minimal land and freshwater requirements. Geothermal stations use 404 square meters per GWòh versus 3,632 and 1,335 square meters for coal facilities and wind farms respectively. They use 20 litres of freshwater per MWòh versus over 1000 litres per MWòh for nuclear, coal, or oil. Geothermal power stations can also disrupt the natural cycles of geysers. For example, the Beowawe, Nevada geysers, which were uncapped geothermal wells, stopped erupting due to the development of the dual-flash station.

Geothermal power requires no fuel; it is therefore immune to fuel cost fluctuations. However, capital costs tend to be high. Geothermal power is highly scalable: a small power station can supply a rural village, though initial capital costs can be high. It is therefore necessary to explore the possibility of setting up more geothermal power plants to use the naturally occurring renewable source of energy.

Pricing Challenges
Unlike traditional power plants that run on fuel that must be purchased over the life of the plant, geothermal power plants use a renewable resource that is not susceptible to price fluctuations. But, although the cost of generating geothermal has decreased by 25 per cent during the last two decades, exploration and drilling remain expensive and risky.

New geothermal plants currently are generating electricity from $0.05-0.08 per kilowatt hour (kwh). Once the capital costs have been recovered price of power can decrease below $0.05/kwh.

However, all things taken into account, the price of geothermal is within range of other electricity choices available today when the costs of the lifetime of the plant are considered.

Prospects of geothermal energy in India
India has huge potential to become a leading contributor in generating eco-friendly and cost effective geothermal power. Around 6.5 per cent of electricity generation in the world would be done with the help of geothermal energy and India would have to play a bigger role in the coming years in this direction. But, the power generation through geothermal resources is still in nascent stages in India.

Puga, which is located at a distance of about 180 km from Leh in the Ladakh region of Jammu and Kashmir across the great Himalayan range, is considered to be a good potential of geothermal energy. In Puga valley, hot spring temperatures vary from 30oC to 84oC (boiling point at Puga) and discharge up to 300 liters /minute. A total of 34 boreholes ranging in depths from 28.5 m to 384.7 m have been drilled in Puga valley. Thermal manifestations comes in the form of hot springs, hot pools, sulphur condensates, borax evaporates with an aerial extent of 4 km. The hottest thermal spring shows a temperature of 84oC and the maximum discharge from a single spring is 5 liters /second.

The thermal water from Chhumathang is quite similar to the thermal waters at Puga except the difference that its water has relatively higher pH and sulphate. Geothermal activity at Manikaran occurs in the form of hot springs over a distance of about 1.25 km on the right bank of Parvati river with a temperature range of 34oC-96oC, whereas on the left bank over a distance of about 450 m with a temperature range of 28oC-37oC.

At Tapovan geothermal area, the highest temperature recorded is 65oC. The discharge from this spring varies between 0.83-9.2 litre/second. Similarly, Tattapani is a promising geothermal resource in Peninsular India. Thermal manifestation at Tattapani is very intense in an area of 0.05 sq. km with several hot spots, hot water pools and marshy land. The surface manifestations show occurrence of white to dirty white deposits identified as silica and moderate to low sag activity.

Sixty thermal water springs occur at eighteen localities in the West Coast hot spring belt. One geothermal power project has a capacity of 25MW. Himurja, Himachal Pradesh has decided to select some geothermal resources in Beas valley, Parvati valley, Satluj valley and Spiti valley in Himachal Pradesh for deep drilling up to 2 km for exploitation of geothermal energy.

India 1st Geothermal Plant

Chhattisgarh Chief minister Raman Singh has said that India’s very geo-thermal power project will be established at Tatapani in the state. According to Raman, the project will use the underground hot water springs at Tatapani to convert it into steam, and then generate it into electricity. Singh said the government had signed a MoU with NTPC on February 16, to construct the project, and the state’s Renewable Energy Development Agency (CREDA) and NTPC are working jointly towards the implementation of the project, which will have varied uses, e.g. electricity generation, heating, drying applications, melting of snow and ice on roads in winter, sterilisation etc. India is said to have an estimated 10,600 MW of potential in the geothermal provinces.


Barriers

  • Finding a suitable build location.Energy source such as wind, solar and hydro are more popular and better established; these factors could make developers decided against geothermal.
  • Main disadvantages of building a geothermal energy plant mainly lie in the exploration stage, which can be extremely capital intensive and high-risk;many companies who commission surveys are often disappointed, as quite often, the land they were interested in, cannot support a geothermalenergy plant.
  • Some areas of land may have the sufficient hot rocks to supply hot water to a power station, but many of these areas are located in harsh areas of the world (near the poles), or high up in mountains.
  • Harmful gases can escape from deep within the earth, through the holes drilled by the constructors. The plant must be able to contain any leaked gases, but disposing of the gas can be very tricky to do safely.

Jocelyn Fernandes

Sourced from: Geological Survey of India, Ministry of Mines, Government of India; Energy Alternatives India (EAI); Authored Article by Oum Prakash Sharma, Deputy Director, and Poonam Trikha Consultant, at National Centre for Innovations in Distance Education, Indira Gandhi National Open University, New Delhi.

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