Geothermal Energy in India – UPSC

• Geothermal energy is the natural heat of the earth’s interior, used both to generate electricity and to warm buildings directly.
• It is a renewable, round-the-clock source tied to place: the richest fields follow plate margins, rift zones and young mountain belts.
• India’s resource is mapped at about 10 GW, but the country has no commercial geothermal plant yet. Its work so far consists of pilots, drilling at Puga in Ladakh and a first national policy (2025).

Geothermal Energy as a Resource

Source of the Heat

• The heat lies in the crust and mantle and is renewed mostly by the decay of naturally radioactive elements such as uranium and potassium.
• Magma, or molten rock, occurs beneath the crust in pockets and melt zones. It does not form a continuous molten layer, since the mantle as a whole is solid rock that creeps slowly.
• The store is enormous. The top 10,000 metres (about 33,000 feet) of the earth holds an estimated 50,000 times the energy of all the world’s oil and natural gas resources.
  • Only a tiny fraction of this store can be reached at a useful temperature with present technology.
• Geothermal gradient is the rise of temperature with depth in the crust. Its average is about 2.5–3°C per 100 m.
  • Usable systems occur where the gradient is normal or slightly above normal.
  • They are best developed around plate margins, where the gradient can far exceed the average.

Types of Geothermal Resource

• The resource falls into three major categories. Only one is worked commercially.

• A second division goes by enthalpy, or usable heat content, and sets the use of a site:
  • High enthalpy (geysers, hot springs, volcanic regions): suited to electricity.
  • Low to medium enthalpy (hot rocks, shallow ground): suited to direct use such as heating, cooling, food processing and fish farming.

Natural Expressions

• The heat reaches the surface in several natural forms:
  • Geysers
  • Lava fountains
  • Hot springs

Harnessing the Heat

How It Is Captured

• The usual method taps a hydrothermal convection system. Cool water sinks through the crust, picks up heat and rises again, and wells bring it up as hot water or steam to spin turbines.
  • The first such power plant was built in Italy in 1904.
• Three plant designs are in use:

• The numbered stages in this figure run: hot water rises (1), steam separates (2), the turbine and generator run (3), the cooling tower condenses the fluid (4), and the injection well returns it underground (5).
• Enhanced geothermal systems (EGS) create a reservoir where nature has not. Water is forced into deep hot rock to open fractures, and the heated fluid is drawn back through other wells.

• This figure shows an enhanced system, in which injected fluid raises the permeability of the rock. A natural hydrothermal field needs no such stimulation.
• Direct use needs no turbine at all: space heating, greenhouses and cold storage, fish farming, tourism and ground source heat pumps, which use stable underground temperatures for heating and cooling.
• World capacity stood at about 15.4 GW at the end of 2024, led by the United States, Indonesia and the Philippines.

Advantages

• Renewable: the heat radiating from the earth’s interior is taken to be enough for human demand for all foreseeable time, provided each field is well managed.
• Easy to exploit in some cases: people have long used hot water to bathe, warm homes and cook. Direct heating of homes and offices continues, and it is cheap where the resource lies close to users.
• Low carbon dioxide output: far less than fossil fuel, which eases both global warming and local air pollution. The output is low but not zero, as the disadvantages below show.
• High net energy yield: modular units can be added as demand grows, and generating costs come close to those of conventional sources.
• Steady supply: it runs as baseload power at capacity utilisation factors above 80%, whatever the weather or the hour.

Disadvantages

• Not available everywhere: hot spots are scattered and often far from the places that need the energy.
• Hydrogen sulphide (H2S): this “rotten eggs” gas can escape in large quantities and is fatal if too much is inhaled.
• Water pollution: extraction can contaminate water, somewhat as mining does.

Challenges

• Resource and location:
  • Heat underlies the whole planet, but only a small share of the land sits over usable pockets of water and steam.
  • Many ideal sites are tectonically very active, and the risk of earthquakes or eruptions deters firms from building large plants.
• Location limit: this is the largest single drawback. Plants must be built where the heat is, so countries such as Iceland gain while many regions cannot use it.
• Infrastructure:
  • Lack of adequate infrastructure has held back geothermal electricity even in the United States.
  • It has traditionally served only the baseline of a grid, which raises problems of its own.
  • Drilling rigs and plants are very costly, and training staff takes time and money.
• Transmission barrier:
  • Steam or hot water cannot sensibly be piped more than about two miles, so energy is used where it is extracted and cannot be diverted to a grid in greater need.
  • Many good fields are rural, and new power lines are expensive and hard to site.
• High cost: a plant costs roughly $2–$7 million per megawatt. The heavy upfront outlay can be recovered as a long-term investment.
• Renewable does not mean unlimited:
  • Each well holds a finite amount of water and steam.
  • Without reinjection, pressure falls and output dwindles, and geological damage such as sinkholes may follow.
• Sustainability: fluid has to return to the reservoir at a rate that keeps pace with extraction, so each field needs careful management. Industry has to weigh these gains and risks together.
• Environmental side effects:
  • Plants do not typically release greenhouse gases of their own, but drilling frees gases stored underground.
  • Their release is natural too, yet its rate rises near plants, though it stays far below that of fossil fuels.
  • Radioactive gases can escape through drill holes, so a plant has to contain leaks and dispose of them safely.
• Earthquakes:
  • Altering rock at depth can trigger tremors, above all in enhanced systems.
  • Examples: a magnitude 3.4 quake at Basel, Switzerland (2006) and a magnitude 5.4 quake at Pohang, South Korea (2017), which a government panel linked to an experimental plant.
  • Most plants lie far from cities, which usually limits the harm, but Pohang shows this is not always so.

Geothermal Energy in India

Exploration and Resource Base

• Exploration and study of geothermal fields began in India in 1970.
• Satellites such as IRS-1 have helped, through infrared imagery, to locate geothermal areas.
• The count of localities has grown with surveys:
  • Older counts by the Geological Survey of India (GSI) give about 340 hot spring localities, and around 350 geothermal locations in some tallies.
  • The National Policy on Geothermal Energy (2025) works from 381 hot springs, with surface temperatures of 35°C to 89°C. Older surveys describe many springs as close to boiling point.
• Reservoirs in the Himalayan belt approach 200°C. The rest of India is mostly a medium to low enthalpy zone (100–180°C).
• Potential: GSI mapping gives a broad estimate of about 10 GW, cited by the Ministry of New and Renewable Energy (MNRE), and often stated as 10,600 MW.
  • Individual estimates are much smaller: 4–5 MW at Puga in older accounts, about 17 MW at Tattapani (GSI, 2016) and up to 122 MW at Manuguru (2024).
• The most promising single field is the Puga valley of Ladakh, on the Indus suture zone.

Geothermal Provinces

• India was long divided into 7 geothermal provinces. The 2025 policy maps 10, adding the north-east and the islands and the southern craton.

Major Sites

• This map uses four legend classes only. The Godavari and Mahanadi basins share the colour of the Son-Narmada-Tapi lineament, though they are counted as separate provinces.

• The provinces on this map are the older ones. Puga lies in the Union Territory of Ladakh (since 2019), Odisha was earlier called Orissa, the Godavari belt falls largely in Telangana and Andhra Pradesh, and Dadra and Nagar Haveli and Daman and Diu have been one Union Territory since 2020.

Projects and Pilots

• Puga’s earlier drilling drew criticism after an uncontrolled discharge. The valley is a fragile high-altitude wetland and grazing area, so reinjection and water handling matter as much as output.
• Surveys for direct heat and power have also gone on at sites in Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Jharkhand and Chhattisgarh.

Government Initiatives

• National Policy on Geothermal Energy, dated 15 September 2025, and the first of its kind:
  • It backs power generation, direct use and ground source heat pumps, within the net-zero 2070 goal.
  • It promotes enhanced and advanced systems, solar-geothermal hybrids and the reuse of abandoned oil and gas wells.
  • It provides for a geothermal data repository, a single-window system for clearances and centres of excellence.
  • States may allot sites for exploration for three years, extendable by two, with two further years in high-altitude areas.
  • Tax holidays, duty exemptions, concessional loans and viability gap funding are under consideration, not yet in force.
• Five projects sanctioned by MNRE, as a first step:
  • 450 kW binary plant from retrofitted oil and gas wells (IIT Madras).
  • Resource study and Army base heating in the Arunachal Himalaya.
  • Solar-geothermal hybrid plant (Pandit Deendayal Energy University, Gujarat).
  • Shallow geothermal potential map and heat pump standards (IIT Delhi).
  • Geothermal cooling of rooms (Osmania University).
• Earlier support: a capital subsidy of up to 30% was planned for industrial projects, and MNRE gives incentives and subsidies for Research, Design, Development and Demonstration (RDD&D).
• Missed target: MNRE planned 1,000 MW by 2022. India’s commercial capacity remained nil in mid-2026, because of drilling cost, technical complexity and the remoteness of its best fields.