Geothermal Energy Resources of India

                               ( IBC Conference "Geothermal Power Asia 2000" Manila, Philippines, Feb.2000)

D. Chandrasekharam
Professor and Head Department of  Earth Sciences
Indian Institute of Technology, Bombay, India

Abstract

Indian geothermal provinces have the capacity to produce 10,600 MW of power- a figure which is five time greater than the combined power being produced from non-conventional energy sources such as wind, solar and biomass. But yet geothermal power projects have not seen the sunlight due the availability of 192 billion tones of recoverable coal reserves. With escalating environmental problems with coal based projects, Indian  has to depend on clean, cheap, rural based and eco-friendly geothermal power in future. Due to technical and logistic problems with other non-conventional energy sources, present industrialists mood is upbeat and IPPs are showing keen interest in developing geothermal based power projects. With the existing open economic policies of the Govt., and large incentives given to non-conventional energy sectors,  the future of geothermal energy sector in India appears to be bright.

Introduction

Several geothermal provinces in India characterized by high heat flow (78-468 mW/m2) and  thermal gradients (47-100^o C/km) discharge about 400 thermal springs. After the oil crisis in 1970s, the Geological Survey of India conducted reconnoiter survey on them in collaboration with UN organization and reported the results in several of their records and special publications ( G.S.I., 1987; G.S.I.,1991). Subsequently, detailed  geological, geophysical and tectonic studies on several thermal provinces (Kaila and Krishna, 1992; Gupta, 1981; Ravi Shanker, 1988) geochemical characteristics of the thermal discharges and reservoir temperature estimations  have been carried out by several workers ( Giggenbach, 1976;  Giggenbach et.al., 1983; Nevada and Rao, 1991; Chandrasekharam et.al., 1989; 1992; 1996;  Chandrasekharam and Antu, 1995; Chandrasekharam and Jayaprakash, 1996; Chandrasekharam et.al., 1997 ).  These investigations have identified several sites which are suitable for power generations well as for direct use. These provinces are capable of generating 10,600 MW of  power (Rani Shanker, 1996). Though  geothermal power production in Asian countries like Indonesia, Philippines has gone up by 1800 MW in 1998,  India with its 10,600 MW geothermal power potential is yet  appear  on the geothermal power map of the world!  Availability of large recoverable coal reserves and a powerful coal lobby is preventing healthier growth of non-conventional energy sector, including  geothermal. However, with the growing environmental problems associated with thermal power plants, future for geothermal power in India appears to be bright. Several IPPs engaged in  non-conventional energy projects are frantically searching for foreign financial institutions to develop geothermal based energy sources. The present status of non-conventional energy sources, problems associated with coal based thermal power projects,  power generating potential of certain important geothermal provinces  and  opportunities for financial institutions in India are discussed in the present paper.

Present status of non-conventional energy resources

The estimated power shortage in India in the next five years is about  43,000 MW. This demand will increase in the coming years due to economic globalization.  Though India boasts of generating eco-friendly energy sources during the coming millennium, the present  power generated through non-conventional sources is far less than the installed capacity of the power plants (Table 1). Thus the total installed capacity from renewable stands at 1313 MW which is 2.6 % of the total potential.  Though capital subsidy and financial incentives are given by the Govt. of India, non-conventional energy  sources are not able to bridge the gap between demand and supply of power. Geothermal energy, a non-conventional energy source, has not so far put to use though its  power generating capacity is of the order of 10,600 MW.  Neither the Govt. bodies nor the independent power producers (IPPs) are aware of this vast resource in the country.  When non-conventional energy sources have the potential of generating about 60,600 MW power, which is more than the required amount for the next five years, then why Indian is not keen in developing this source in bridging supply-demand power gap?  The answer lies in the 192 billion tones of recoverable coal reserves which is encouraging coal based power projects  and hampering the healthy growth of  non-conventional energy programs. In addition to coal, availability of naphtha in the world is adding fuel to the fire!.

       Table 1. Power production status  of non-conventional energy in India

 Power generating capacity of  Indian geothermal provinces

Indian has 400 medium to high enthalpy geothermal springs, clustered in seven province shown in Figure 1. The most promising provinces are    i)   The Himalaya,  ii)  Sohana,  iii)   Cambay,   iv)  Son-Narmada-Tapi (SONATA) and v) the Godavari.  With the recent volcanic eruption, the Barren island, a part of the Andaman-Nicobar chain of islands, is added to the above list. Most of them are liquid dominated systems with one or two having both liquid and gas dominated systems. Let us examine the geothermal  characteristics of some of the  provinces.

The Himayala Province:

This is one of the most promising provinces in the coldest part of the country and contains about 100 thermal springs with surface temperatures as high as 90^o C discharging > than 190 tones /h of thermal water. This province falls in one of the most tectonically active zones- the Indo-Eurasian plate boundary (Fig. 1) which experiences a large number of earthquakes ( Chamoli experienced 6.8 magnitude earthquake on 29, March 1999).  Post Tertiary granite intrusives are responsible for the high temperature gradient ( > 100^o C/km) and heat flow (> 468 mW/m²) recorded  in the 500 m drill-hole in this province. Geothermal reservoir between depths 1 and 3 km was delineated from magneto-telluric recordings ( Singh and Nabetani, 1995).  The first and the last (!) pilot binary  5 kW power  plant using R 113 binary fluid was successfully operated by the Geological Survey of India at Manikaran which proved the power producing  capability  of this province. Presence of epidote in drill-cuttings recovered from 500 m drill-holes support estimated reservoir temperature of  260^o C. Space heating experiments were also successfully conducted using thermal discharge by the Geological Survey of India. 

Cambay Province:

Situated in  a failed arm of a rift (Sheth and Chandrasekharam, 1997), this province forms a part of the Cambay basin with > 500 m of post Cretaceous sedimentary formation overlying the well known Deccan flood basalts. Besides  deep seated faults, which brackets the basin,  older  granite intrusives ( ~ 955 Ma; Gopalan et. al., 1979), such  as  those at Tuwa and Miocene- Pliocene basic intrusives, contribute  partly to the  high  thermal gradient ( > 60^o C) and heat flow value ( >80 mW/m²) of this basin. More than 15 thermal discharge sites are located in this province with surface temperatures varying from  40 to 90^o C. Steam discharge in certain oil wells were recorded with rates exceeding 3000 m³ /d. Reservoir temperatures estimated at two sites (Tuwa and Tulsi Shyam) are greater than 150^o C ( Kamble, 1994).

West coast province:

This province is located within the world famous Deccan flood basalts of Cretaceous age. Attenuation and foundering of the continental crust  prior to the outpouring of the large volume of lavas along the coast (Chandrasekharam and Parthasarathy, 1978) resulted in the development of several faults and graben structures (Chandrasekharam, 1985) which are channeling thermal waters. This province enjoys a thin lithosphere of 18 km thickness ( Pande et.al., 1984) thereby rendering this province as one of the most promising sites for exploitation. The thermal discharges are saline with Cl content varying from 800 ppm to little over  1500 ppm ( Ramanathan, 1993). Hence, geothermometers may not indicate the true reservoir temperatures. About 1% saline component has been estimated in these thermal discharges. The reservoir temperatures calculated, after making necessary correction for 1% saline component, are between 102 and 137^o C (Chandrasekharam et.al., 1989). One thermal discharge, located at Rajapur, within the Deccan basalts along the coast is an exception to the other thermal discharges mentioned above. The thermal reservoir of this discharge is located within the Precambrian formation, like the Puttur thermal waters, with reservoir temperatures varying between 120 and 200^o C ( Ramanatha and Chandrasekharam, 1997).

SONATA province:

This province extending from Cambay in the west to Bakreswar in the east is an area with very high heat flow and geothermal gradient (Fig. 1) and encloses the well known Tattapani geothermal province spreading over an area of about 80,000 sq.m. The Tattapani province encloses 23 thermal discharge sites with surface temperatures varying between 60 and 95^o C and flow rate greater than 4000 l/m..  Nine thermal springs are discharging waters at 90^o C. These waters, compared to those of west coast, are low in Cl content ( 60 - 70 ppm) and the chemical composition of the thermal discharge is controlled by water-rock interaction. Based on thermal gradient and experimental results, estimated reservoir temperatures are as high as 217^o C at 3 km depth. (Chandrasekharam and Antu, 1995). In certain bore holes drilled by the Geological Survey of India, thermal discharge was not encountered but the recorded thermal gradient in these bore holes exceed 100^o C/km (K. Muthuraman, G.S.I., personal communication). Such  sites are best suited for experimenting HDR projects ( Chandrasekharam, 1996). Five 6 inches diameter production wells to commission a pilot power plant of 3.17 MW  were drilled by  the GSI. The pressure of the thermal discharge is 5 kg/cm² and the estimated life of the reservoir is about 20 years ( Pitale et.al., 1995). It is unfortunate that a power plant is yet to be commissioned at Tattapani!!

Unapdeo and Nazardeo, the two thermal provinces located between Tattapani and Cambay and enclosed by the Tapi rift within the SONATA, discharge 59^o C  thermal waters. Though these springs issue through Deccan basalts, chemical signature of the springs indicate that they are in chemical equilibrium with underlying Na-rich granites, recorded through magneto-telluric surveys (Rao, et.al., 1995). Estimated reservoir temperatures are 105 and 133^o C respectively.  (Chandrasekharam and Prasad, 1998).

Bakreswar province:

The Bakreswar-Tantloi thermal province falls in Bengal and Bihar districts and marks the junction between SONATA and Singbhum shear zone (Fig. 1). High He gas is encountered in all the thermal discharges (water and gases) and it is proposed to install a pilot plant to recover He from the thermal manifestation of this region. The He discharge is  4 l//h ( Nagar et.al., 1996).

Godavari province:

Godavari valley in Andhra Pradesh is a northwest-southeast trending graben filled with Gondwana sedimentary formations. The lower Gondwana group of roks consist of sandstone, shale and clays and are exposed towards the southwestern part of the graben and hosts 13 thermal discharges with surface temperature varying from 50 to 60^o C. This graben falls within zone II (100 - 180 mWm²) on the heat flow map of  India and  has  a thermal gradient of 60^o C/km (Ravi Shanker, 1988). Two thermal springs, Bugga and Manuguru, discharging 1000 l//m of water, were studied in detail. Talchir sandstone, which forms a unit in the lower Gondwana group, is the reservoir rock with an effective porosity of 35%. The storage capcity of the sandstone is 35 x 10⁶ m³ which is expected to yield thermal discharge for about 75 years. Geochemical thermometers indicate reservoir temperatures in the range of  175 and 215^o C. The reservoir is reported to be at a depth of 2.5 km. It has been estimated that 38 MW power can be generated from this province (Chandrasekharam and Jayaprakash, 1996). A 1-6 shell and tube heat exchanger to suite the thermal discharge conditions has been designed to dehydrate 10,000 lb/hr of onions with an air volume of 20,000 m³ (Chandrsekharam et.al., 1996).

The Barren island:

The Barren island forms a part of the Andaman - Nicobar island chain in the Bay of Bengal and is located 116 km ENE of Port Blair. Recent volcanic activity was recorded in 1991 which resulted in the appearance of high temperature steaming ground and thermal discharges. Fumarolic discharge recorded temperatures varying between 100 and 500^o C. Detailed exploration work needs to be commissioned in this province.

Table 2. summarizes the temperatures, heat flow values and geothermal gradients of the provinces discussed above. 

Table 2.  Potential Geothermal provinces  of  India

Thus, it is apparent that, with the available technology all the above thermal provinces can be exploited for power generation as well for direct use.

Problems with  conventional and non-conventional power projects:

Though coal based and naphtha based power project are riding over other non-conventional energy sources, environmental problems associated with such mega-projects are many. India’s 67,000 MW of thermal power generating capacity constitutes about 70% of the country’s total power generation capacity. Due to oil shocks of 1970s, oil-fired power generation has come down to 15%. This has increased the dependence on coal based power projects due to 192 billion tones recoverable coal reserves available with India. Both oil-based and coal based power projects have similar environmental problems. Indian is already the sixth largest and second fastest growing contributor to greenhouse gases. Emissions of nitric oxide, sulphur dioxide and particulate matter is expected to treble in the next decade. The greatest unsolved problem with coal based power plants is the fly-ash.  Indian coal has an ash content of 45 %. In contrast to most of the other (developed?) countries, which stopped promoting coal based thermal plants,  these thermal power plants are thriving in India  producing 75 million tones of fly-ash!!  This production is expected to grow to 100 million tones in the next millennium. Only 3 % of this is being utilized! If all the bricks in the country were to be made of fly-ash, only 5%  of  75 million tones  will be put to use ( Business World, 1998). These toxic emissions are ruining historical monuments, such as the Taj Mahal. Based on a public interest petition, Supreme court has ordered  to stop burning coal in and around Taj Mahal.  Naphtha based power project, like that commissioned in Dhabol in Maharashtra and like that going to be commissioned in Karnataka in collaboration with American based ABB company, are going to be no better than coal based power projects as far as protecting the environment is concerned!!

Besides this, due to other problems related to transmission and distribution of power, whose losses estimated to be about 23 %,  power generation has fallen short by 53%.  To solve these problems, M/s Energy Line Systems of Alameda, California, a subsidiary of S&C Electric company, Chicago, in collaboration with the Karnataka Electricity Board will conduct  a pilot project in Karnataka to provide affordable, reliable and efficient energy supplies and services (Economic Times, 8 June 1999).

This doesn’t mean that  non-conventional power projects are free from such problems. They have problems of different kind. Solar Photovoltaic source, though has potential of 20 MW/km²,  is generating only 810 KW ( Table 1.). Though incentives to promote this source is offered by the Govt., import cost of the cells is retrograding the development (Mr.Avinash Brahmabhatt, M/s Avin Energy Systems, Ahmedabad, Personal communication). Indian has to develop indigenous technology to support this source of energy.

Similarly, a large number of incentives in term of soft loans from IREDA, tax holidays, exemption  from custom duty etc. are given to wind energy developer. With all these incentives, during the ninth plan, this source is expected to add a meager  1000 MW more of power to the country’s demand!!

In the case of hydro power, the potential and achievement figures shown in table 1. certainly indicate that this is a highly neglected sector both by the policy  makers as well by the IPPs. In  a recent statement, the Chairman, National Hydro Power Corporation, mentioned that the hydro power sector has a potential of generating 84, 000 MW at 60% load factor equivalent to 1,48,700 MW of installed capacity. This figure  when compared to that  in table 1, shows optimism of the Chairman, NHPC. The bulk of the hydro power potential is concentrated in northwestern and northeastern regions of the country and demand for power is far less in the states surrounding this region like the Himachal Pradesh, Jammu and Kashmir. These states have no resources to develop this sector. IPPs are not interested in investing in this sector due to inadequate government policies in areas like fuel linkage, acquisition of project site, poor financial status of state electricity boards, lack of financial resources within the Indian financial institutions to support proposed power projects (Economic Times, 2 June, 1999).

But financial Institutions have adequate resources to finance coal and naphtha based projects!! Take for example Enron’s Dabhol project in Maharashtra or 615 MW naphtha-based power plant being set up in Pipavav, Gujarat in collaboration with KRIBHCO or 375 MW lignite based power plant at Ghoga, Gujarat for which offers have been invited or  the 420 MW thermal power plant being setup by AES Transpower  in Orissa’s Ib valley.  These figures indicate the existence of a very strong coal lobby which is hampering the healthy growth of  non-conventional energy sources. It is surprising, why India till date is unable to tap the 10,600 MW  geothermal energy based power!. Financial assistance  is needed  to develop geothermal resources  in  the face  of   stiff  (Coal) competition in India. 

What are the opportunities to develop geothermal energy resources?

Of late, IPPs involved in non-conventional energy sources, are showing keen interest in Geothermal energy resources, thanks to the awareness brought by those organizations working in this field  such as the IITs  ( Chandrasekharam, 1995) and  the GSI. One-time investment and low maintenance cost, low area requirement, and incentives given by the Govt. for non-conventional energy sector is attracting many IPPs in India. Even  IPPs who are involved in solar Photovoltaic and solar thermal power business are frantically exploring partners to finance geothermal projects. For example, M/s Avin Energy Systems, who are involved in solar Photovoltaic and solar thermal prewar projects, are keen to develop geothermal projects in Gujarat and expand their activities to other states as well. Since all the thermal provinces are located in rural areas  with excellent  communication system, power projects as well geothermal based industries are going to reduce  congestion in Urban areas and improve socio-economic status of the rural public.

Concluding remarks:

With escalating environmental problems with coal based project, non-participation of IPPs in hydro power projects, logistic and technical problems clouding other non-conventional  energy projects, in future, India has to depend on clean, rural based, cheap energy sources and can not ignore its 10,600 MW geothermal potential. With available advance technology, all the medium enthalpy resources can be developed to support binary power projects. Compact generators like those developed by M/s Sowit and Turboden, Italy ( Angelino et.al., 1995) or like those developed by NEDO, Japan,  are most suitable for generating rural based power from various thermal provinces. Till recently IPPs are not aware of geothermal resources of the country due to lack of awareness and mass communication. Conferences like  the one conducted here, should be organized in India with major industrial participation. Like M/s Avin Energy Systems, foreign participation in geothermal sector will attract other Indian IPPs also. Alternatively, foreign IPPs can participate in power projects under “Build-Own-Operate-Maintain”(BOOM) scheme. Commissioning of at least one geothermal based power project is going to change the entire future  power scenario of India. What is need at present is a project to drill deep holes and  initiate studies on reservoir modeling. Data on thermal gases is lacking till now. But under  the present ongoing collaborative project between India and Italy, systematic geochemical investigation on thermal gases is being carried out (Minissale et al., 2000).

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_____________________________________________________________________________

Prof. D. Chandrasekharam,
Head, Department of Earth Sciences, Indian Institute of Technology,
Bombay 400076. Ph: 572 6568; email: dchandra@geos.iitb.ac.in
For more information  on Indian geothermal provinces see: web: http://www.geos.iitb.ac.in/dchandra