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^oC/km) discharge about 400 thermal springs. After the oil crisis in 1970s, the Geological Survey of India conducted reconnoiters 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 (see table below). 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 powers, 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 shows power production status of non-conventional energy in India

(Chandrasekharam, 2000)

Power generating capacity of Indian geothermal provinces
India has 400 medium to high enthalpy geothermal springs, clustered in seven province shown in the figure given below. 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 these provinces.

The Himalaya 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^oC discharging > than 190 tones/h of thermal water. This province falls in one of the most tectonically active zones- the Indo-Eurasian plate boundary (see fig. below) 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^oC/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^oC. 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^oC) 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^oC. 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^oC ( 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^oC (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^oC ( 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 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^oC and flow rate greater than 4000 l/m. Nine thermal springs are discharging waters at 90^oC. 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 217o 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^oC/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^oC 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^oC 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(see figure below). High helium (He) gas is encountered in all the thermal discharges (water and gases) and it is proposed to install a pilot plant to recover helium 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 rocks consists 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^oC. This graben falls within zone II (100 - 180 mW/m²) on the heat flow map of India and has a thermal gradient of 60^oC/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^oC. 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 500o C. Detailed exploration work needs to be commissioned in this province. 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.

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

Heat flow: mW/m²; Thermal gradient: ^oC/km

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 (above table). Though an incentive 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 power production table, 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 power 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).

Map showing Indian geothermal provinces with heat flow and geothermal gradients

Top