Energy, the geothermal way ASHOK B SHARMA Posted: Oct 07, 2008 at 2233 hrs IST Updated: Oct 07, 2008 at 2233 hrs IST
Geothermal energy is an alternative renewable source of energy, derived from natural heat stored in the deep interior of the earth. In the last few decades there is an increase in the use of geothermal energy all over the world, both for power generation and direct heat applications.
There is a total globally installed geothermal capacity of over 8,900 MWe for power generation and 27,825 MWt for non-electrical purposes, according to the data available till 2005. Largest users of geothermal energy are US, Philippines, Italy, Mexico, Iceland, Indonesia, Japan and New Zealand. World over the most common non-electrical uses of geothermal energy in terms of installed capacity are heat pumps (33%), bathing (29%), space heating (20%), greenhouses (7.5%), aquaculture (4%) and industrial processes (4%).
In power generation from geothermal energy, US is a major producer with 2,544 mw reported in 2005, followed by Philippines with 1,931 mw, Mexico with 953 mw, Indonesia with 797 mw, Italy with 790 mw, Japan with 535 mw, New Zealand with 435 mw, Iceland with 202 mw, Costa Rica with 163 mw, El Salvador with 151 mw, Kenya with 127 mw, Russia with 79 mw, Nicaragua with 77 mw, Guatemala with 33 mw and China with 28 mw. Besides there are nine other countries generating power from geothermal energy.
India has made a humble beginning by conducting explorations & surveys and identifying 340 perennial hot springs with surface temperature ranging between 37°C & 90°C. However, most of these hot springs are low temperature hot water resources and can be utilised for direct heat applications. Only a few of them are suited for of about 10,000 mw. The hot springs identified in the country are grouped into seven zones:
* Himalayan-Puga Chhumthang
* Sohana valley
* Cambay basin
* Son-Narmada lineament belt
* West Coast
* Godavari basin
* Mahanadi basin.
Geothermal explorations carried out so far have generated data through extensive scientific studies backed by drilling at selected sites like Puga, Manikaran, Tatapani, Tapovan and Cambay. The data generated relate to structural, geological, geo-chemical, hydrological and thermal parameters.
An experimental geothermal power plant of 5 mw capacity has been set up at Manikaran in Himachal Pradesh. A cold storage plant has also been set up in the area to utilise geothermal energy at 90°C for preserving vegetable and fruits. The Jammu-based Regional Research Laboratory has taken up an R&D project for harnessing geothermal energy in Puga valley for mushroom cultivation and poultry farming. A 30x20 feet insulated hut has been constructed and temperature maintained in the range of 20°C to 25°C. A pre-feasibility report on development of geothermal fields in the Puga valley for power generation has been prepared by NHPC.
According to surveys and studies conducted by NGRI, Hyderabad geothermal reservoir is found at a depth of about 1.5 to 2 km in the Puga valley. The estimated depth of geothermal reservoir is about 4 to 5 km and the estimated temperature of the deep geothermal reservoir is 200 to 250°C. In Tatapani the geothermal field found at a depth of 3 km has a temperature of about 260°C.
The use of geothermal energy, however, has certain limitations as it may cause some pollution of land and air due to certain dissolved gases. Excessive removal of gas from the deeper regions of the earth may cause some problems in the future.
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