Wind, tidal, ocean and geothermal energy

Detail

1. Wind energy: the basics

• Wind energy is electricity made from moving air. It is pollution-free because nothing is burnt. It is also renewable (it does not run out).
• How a wind turbine works:
• Moving air has kinetic energy (the energy of motion).
• The wind turns the large blades of a wind turbine.

• The blades spin a shaft joined to a generator, which makes electricity.

• Which winds can be used (NCERT Class 12):

• Planetary winds, which blow all year over large belts of the Earth. Examples are the trade winds (blowing towards the equator) and the westerlies (blowing towards the poles in the middle latitudes).
• Monsoon winds, which change direction with the season. In India the south-west monsoon gives the strongest winds from about May to September.

• Local winds such as land and sea breezes. These blow from sea to land by day and from land to sea by night along coasts.

• The best sites have strong, steady winds. These are coasts, mountain passes and open, flat deserts.

2. Wind energy in India: where it is

• Largest cluster: Nagercoil to Madurai (Tamil Nadu)
• Muppandal in Kanyakumari district, at the southern tip of the peninsula (about 8°N), is India's best-known wind farm area.

• Why it is so windy (the Aralvaimozhi gap):

  • The Aralvaimozhi gap is a low pass in the southern end of the Western Ghats.
  • The south-west monsoon wind is squeezed through this narrow gap.
  • Squeezed air speeds up (a funnel effect). The result is strong, steady wind at Muppandal.

• Jaisalmer (Rajasthan) in the Thar Desert is another well-known wind area. Its flat, open land lets wind blow freely.

• Other major states (NCERT): Rajasthan, Gujarat, Maharashtra and Karnataka.
• Gujarat and Tamil Nadu lead in installed wind capacity. Installed capacity means the most power the machines can produce.
• India has the world's fourth-largest installed wind capacity.
• Current size: India's installed wind capacity was 58,520.32 MW (about 58.5 GW) as of 31 August 2026 [3].
• Large hydro stood at 52,064.67 MW on the same date. Wind capacity is now larger than large hydro capacity [3].

3. Offshore wind energy

• Offshore wind energy comes from turbines placed in the sea, away from the coast.
• Why build at sea:
• Nothing blocks the wind at sea, such as hills, trees or buildings.
• So the wind is stronger and steadier than on land.

• Steadier wind gives more electricity from each turbine.

• India's plan:

• The target is 30 GW of offshore wind by 2030.
• The first zones are off the coasts of Gujarat (Arabian Sea) and Tamil Nadu (Gulf of Mannar and Palk Bay side).

• Viability gap funding (VGF) was approved in 2024. VGF is a one-time government grant that covers part of the building cost, so the project's power is cheap enough for electricity companies to buy.

• Legal step: MNRE notified the Offshore Wind Energy Lease Rules, 2023 on 20 December 2023. These rules set how seabed areas are leased to developers [4].

Feature	Onshore wind	Offshore wind
Location	Land: passes, coasts, deserts	Sea, off the coast
Wind	Weaker and less steady (blocked by land features)	Stronger and steadier
Cost	Lower	Higher (needs VGF support)
Indian examples	Muppandal (Tamil Nadu), Jaisalmer (Rajasthan), Gujarat	Zones off Gujarat and Tamil Nadu (2030 target: 30 GW)

4. Tidal energy

• Tidal energy is power from the rise and fall of the sea (tides). The pull of the Moon and the Sun causes tides.
• Tidal range is the height difference between high tide and low tide. A bigger tidal range gives more power.
• How a tidal power plant works (NCERT Class 10):
• A floodgate dam (a dam with gates) is built across a narrow inlet of the sea.
• At high tide, seawater flows in through the gates and is trapped behind the dam.

• As the tide falls, the trapped water flows back to the sea through turbines, which make electricity.

• Best sites in India:

• Gulf of Khambhat (Cambay) and Gulf of Kachchh, both in Gujarat on the west coast. These narrow, funnel-shaped gulfs have very large tidal ranges.

• Sundarbans in the Ganga delta (West Bengal), on the east coast.

• Status: No large tidal plant has been built yet. Proposals have not turned into working plants (NCERT: the potential has "not yet been utilised").

• Wave energy is a related idea. It uses the up-and-down movement of sea waves to drive turbines (NCERT treats tidal and wave energy together).

5. Ocean thermal energy conversion (OTEC)

• Ocean thermal energy conversion (OTEC) makes power from the temperature difference between warm surface water and cold deep water in the sea.
• How it works:
• The Sun heats the top layer of tropical seas. The deep water stays very cold.
• Warm surface water boils a liquid that boils at a low temperature. The vapour spins a turbine.
• Cold water pumped up from the deep cools the vapour back into a liquid. The cycle then repeats.

• It needs a difference of about 20°C between surface and deep water. Only tropical seas have this.

• India's potential:

• About 2,000 km of the South Indian coast has a temperature difference of more than 20°C all through the year [5][6].

• Total OTEC potential around India is estimated at about 180,000 MW [5][6].

• Kavaratti (Lakshadweep) demonstration plant:

• NIOT (National Institute of Ocean Technology, Chennai, under the Ministry of Earth Sciences) is building it.
• It will run Low Temperature Thermal Desalination (LTTD). LTTD turns seawater into drinking water using the warm–cold water difference.
• The planned output is 1 lakh litres of drinking water per day [5][6].
• Islands like Lakshadweep have little fresh water and the deep sea lies close to the shore, so OTEC suits them.

Ocean source	What drives it	Best Indian sites	Status
Tidal	Rise and fall of tides (tidal range)	Gulf of Khambhat, Gulf of Kachchh, Sundarbans	No large plant built yet
Wave	Up-and-down movement of waves	Exposed coasts	Experimental
OTEC	Surface-to-deep temperature difference (about 20°C)	South Indian coast, Lakshadweep	Kavaratti pilot plant (NIOT)

6. Geothermal energy: the basics

• Geothermal energy is heat from inside the Earth.
• Where the heat comes from:
• Radioactive decay of uranium, thorium and potassium. Radioactive decay means unstable atoms slowly breaking down and giving off heat.
• Heat left over from when the Earth was formed [2].

• The core is about 5,000–6,000°C [2].

• Geothermal gradient is how fast temperature rises as you go deeper into the Earth. Where this rise is fast (a high geothermal gradient), hot rock lies close to the surface.

• How it becomes electricity (NCERT):
• Groundwater seeps down and touches hot rocks.
• The water absorbs heat and turns into hot water or steam.
• It rises to the surface as hot springs or geysers (springs that throw hot water and steam into the air from time to time), or it is brought up through wells.

• The steam turns turbines to make electricity.

• After use, the cooled water is pumped back into the underground reservoir. This keeps the supply going [2].

• Why it is useful: it is available round the clock and does not depend on the weather, unlike solar and wind power [2].
• Direct use: the heat can also be used without making electricity, for example to warm homes, farms and fish ponds, and for heating and cooling buildings [2].
• World's first use (NCERT Class 12 box): Boise, Idaho (USA), in 1890. A hot-water pipe network was built there to heat nearby buildings.

7. Geothermal energy in India

• Resource base:
• GSI (Geological Survey of India) has mapped 381 hot springs [2]. (NCERT/earlier: "several hundred hot springs".)
• It has identified 10 geothermal provinces: Himalayan, Naga-Lushai, Andaman and Nicobar Islands, SONATA (Son–Narmada–Tapi rift belt), West Coast, Cambay Graben (a sunken block of crust in Gujarat), Aravalli, Mahanadi, Godavari, and the South Indian Cratonic region [2].

• India's theoretical geothermal potential is about 10.6 GW, with 42 sites found promising for power and direct heat use [2].

• Key sites:

• Manikaran, in the Parvati valley (Kullu district, Himachal Pradesh), has hot springs and an experimental project.
• Puga valley (Ladakh):
  • It lies more than 14,000 feet above sea level in the Himalayan geothermal province [2].
  • In July 2026, the ONGC Energy Centre commissioned India's first two geothermal wells here, each 1,000 metres deep [2].
  • These wells prepare the way for India's first 1 MW demonstration geothermal power project [2].

• Tattapani (Chhattisgarh) is a hot-spring site in central India. Hot springs are also found along the west coast.

• Other government-backed projects (status reported September 2026) [2]:

• Gandhinagar (Gujarat): a project combining solar and geothermal energy. It drilled 3 wells that give fluid at 70–80°C and produced 50–90 kW of electricity.
• Ankleshwar (Gujarat): a test of making electricity by reusing old oil and gas wells.
• Tawang (Arunachal Pradesh): 5 sites are being studied.
• Hyderabad (Telangana): a geothermal cooling system for air conditioning is being developed.

• MNRE sanctioned 5 research projects in July–August 2025.

• Policy:

• The National Policy on Geothermal Energy was notified in September 2025. MNRE is the nodal ministry, meaning the ministry in charge of carrying it out [2].
• The policy supports exploration, drilling, reuse of old oil and gas wells, and ground source heat pumps. These pumps use the steady temperature just below the ground to heat or cool buildings [2].

• It supports India's goal of Net Zero by 2070 [2].

• Global picture: world geothermal capacity was 15.67 GW at the end of 2025. Indonesia, the USA, the Philippines, Türkiye and New Zealand together hold about 67% of it [2]. All five lie in tectonically active zones, mostly on the Pacific Ring of Fire (the belt of volcanoes and earthquakes around the Pacific Ocean).

• No commercial geothermal power plant runs in India yet [2].

Prelims Hooks

• Muppandal (Kanyakumari district, Tamil Nadu) gets winds funnelled through the Aralvaimozhi gap in the southern Western Ghats. India's largest wind cluster runs from Nagercoil to Madurai.
• Leading wind states: Gujarat first, Tamil Nadu second. India is fourth in the world in installed wind capacity. Capacity was about 58.5 GW in August 2026 [3].
• Offshore wind: target of 30 GW by 2030. The first zones are off Gujarat and Tamil Nadu. The Offshore Wind Energy Lease Rules came in 2023 [4], and VGF was approved in 2024.
• Best tidal sites: Gulf of Khambhat and Gulf of Kachchh (Gujarat, west coast) and the Sundarbans (West Bengal, east coast). No large tidal plant has been built in India yet.
• OTEC needs a surface-to-deep temperature difference of about 20°C. NIOT's pilot plant is at Kavaratti (Lakshadweep) and will make drinking water using LTTD [5][6].
• Site–state pairs: Manikaran → Himachal Pradesh (Parvati valley); Puga → Ladakh; Tattapani → Chhattisgarh; Gandhinagar and Ankleshwar geothermal projects → Gujarat [2].
• First geothermal wells in India: Puga valley, by the ONGC Energy Centre, in July 2026 [2].
• India's geothermal facts: GSI has mapped 381 hot springs in 10 geothermal provinces, with a potential of about 10.6 GW. The National Policy on Geothermal Energy was notified in September 2025 [2].
• First use of geothermal energy: Boise, Idaho (USA), 1890.
• Trap: among these sources, only geothermal is round-the-clock and weather-independent [2]. Wind is seasonal, and tidal power depends on the tide cycle.

Mains Points

• Distribution follows physical geography.
• Wind farms gather where relief channels the wind (the Aralvaimozhi gap), on open deserts (Jaisalmer) and along windy coasts (Gujarat).
• Tidal potential is highest in funnel-shaped gulfs on the west coast (Khambhat, Kachchh).
• OTEC suits tropical islands and southern coasts, where the sea is warm all year.

• Geothermal sites follow tectonic belts such as the Himalaya, the SONATA rift and the Cambay Graben [2].

• Role in the 500 GW non-fossil target for 2030:

• Wind (about 58.5 GW in August 2026) [3] is the second pillar of renewable power after solar.
• Wind is seasonal: strong in the south-west monsoon and weak in winter. This makes it hard to keep the power grid balanced.

• Geothermal gives steady base-load power (power that is needed all day and night) and can fill this gap [2].

• Problems:

• Offshore wind is costly and needs VGF, a seabed leasing system [4] and upgraded ports.
• Tidal plants cost a lot and can harm mangroves and mudflats (for example in the Sundarbans and the Gulf of Kachchh).

• Geothermal sites are often remote and at high altitude (Puga is above 14,000 ft) [2], and drilling is risky.

• Policy responses:

• Offshore wind: the Offshore Wind Energy Lease Rules 2023 [4] and VGF approval in 2024.
• Geothermal: the National Policy on Geothermal Energy 2025, reuse of old oil wells, and demonstration projects [2].
• Ocean energy: OTEC-based drinking water for islands that lack fresh water [5][6].