GEO- THERMAL ENERGY

HEMCHANDRA DOLEY (07/154)AMIT ROY (07/150)

MANASH JYOTI BORA (07/328)MAHARNAV GOGOI (07/163)

INTRODUCTION• The word geothermal comes from the Greek words geo (earth) and therme

(heat). So, geothermal energy is heat from within the Earth. We can recover this heat as steam or hot water and use it to heat buildings or generate electricity.

• Geothermal energy is a renewable energy source because the heat is continuously produced inside the Earth.

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From the surface down through the crust, the normal temperature gradient - the increase of temperature with the increase of depth - in the Earth's crust is 17 °C -- 30 °C per kilometer of depth (50 °F -- 87 °F per mile).

Below the crust is the mantle, made of highly viscous, partially molten rocks with temperatures between 650 °C -- 1250 °C (1200 °F -- 2280 °F). At the Earth's core, which consists of a liquid outer core and a solid inner core, temperatures vary from 4000 °C -- 7000 °C (7200 °F-- 12600 °F).

• Major geothermal fields are situated in circum-pacific

margins, rift zones of East Africa, North Africa, Mediterranean basin of Europe, across Asia to Pacific (Figure 1).

Geothermal energy resources•

There are four major types of Geothermal energy resources.

Hydrothermal Geopressurised brinesHot dry rocksMagma

Currently, hydrothermal energy is being commercially used for electricity generation and for meeting thermal energy requirements

Italy, New Zealand, USA, Japan, Mexico, Philippines, Indonesia are some of the countries which are using geothermal energy for electricity generation and thermal applications. Exploration of geothermal fields needs knowledge of geology, geochemistry, seismology, hydrology and reservoir engineering.

• 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 10000 MW.

GEO THERMAL ENERGY AND INDIA

GEO THERMAL ENERGY AND INDIA• Indian organisations working in geothermal energy:

Central Electricity Authority Geological Survey of India Indian Institute of Technology, Mumbai Regional Research Laboratory, Jammu National Geophysical Research Institute, Hyderabad Oil and Natural Gas Corporation, Dehradun

Ongoing Projects in India:

Magneto-telluric investigations in Tattapani geothermal area in Madhya Pradesh Magneto-telluric investigations in Puga geothermal area in Ladakh region, Jammu & Kashmir

Achievements:

Geothermal Atlas of India, prepared by the Geological Survey of India(GSI) gives information/data for more than 300 geothermal potential sitesApplications of geothermal energy for small-scale power generation and thermal applications are being explored.

Potential Applications:

Power generation Cooking Space heating Use in greenhouse cultivation Crop drying

Technology for electricity generationThere are three types of the plants.

1. Dry Steam Power Plants• Dry steam power plants at The Geysers in California.• Steam plants use hydrothermal fluids that are primarily steam. The steam goes directly to a

turbine, which drives a generator that produces electricity. The steam eliminates the need to burn fossil fuels to run the turbine. These plants emit only excess steam and very minor amounts of gases.

2. Flash steam plants When the geothermal energy is available at 150 °C and above temperature, the fluids can be used directly to generate electricity. In some cases, direct steam is available from the geothermal reservoir; otherwise the steam is separated and turbines are used for power generation.

3. Binary plant These plants are used when geothermal temperature is between 100 °C and 150 °C. The fluid is extracted and circulated through a heat exchanger where the heat is transferred to the low boiling point organic liquid. This gets converted into high pressure vapour, which drives organic fluid turbines.

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Direct use of geothermal energy is also possible as shown in the Figure

These systems are useful for heating of houses and living spaces like offices, commercial complexes etc.

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