Tidal energy

Also called: Tidal power, Tidal and wave energy · Topic: Energy Resources of India: Conventional and Non-conventional · NCERT: Class 10, Ch 5 "Minerals and Energy Resources"; Class 11, Ch 13 "Movements of Ocean Water"; Class 12, Ch 5 "Mineral and Energy Resources"

Meaning

Tidal energy is electricity made from the regular rise and fall of sea level (the tides). These are caused by the pull of the Moon and the Sun. A dam with gates traps seawater at high tide and releases it through turbines as the tide falls.

It matters because tides are renewable, pollution-free and arrive on a known timetable. India's west coast has some of the best tidal sites in the country. Even so, no large tidal plant has been built in India yet.

Explanation

Cause: why tides carry energy

• Tides come from gravity.
• The Moon, and to a lesser extent the Sun, pull on the Earth's oceans.

• This makes the sea rise (high tide) and fall (low tide) in a regular rhythm. Most coasts get two high tides and two low tides each day.

• Tidal range is the height difference between high tide and low tide.

• A bigger tidal range means more water moves and falls further, so it gives more power.

• The range is largest during spring tides. These come when the Sun, Moon and Earth are in a line, so their pulls add up.

• Coast shape matters.

• In a narrow, funnel-shaped gulf, the incoming tide gets squeezed between the coasts.
• Squeezed water piles up higher, so the tidal range becomes very large.

Process: how a tidal power plant works (NCERT Class 10)

• Step 1 – Build the dam. A floodgate dam (a dam with gates) is built across a narrow inlet of the sea.
• Step 2 – Trap the water. At high tide, seawater flows in through the open gates and is trapped behind the dam.
• Step 3 – Make power. As the tide falls outside, the trapped water is higher than the sea. It flows back to the sea through turbines, and the turbines make electricity.
• Result: power is produced on a regular, predictable schedule. But it is not produced round the clock, because it follows the tide cycle.

Related type: wave energy

• Wave energy uses the up-and-down movement of sea waves to drive turbines.
• Waves are made by wind blowing over the sea, not by the Moon's pull. So wave energy is a different source from tidal energy.
• NCERT treats tidal and wave energy together as ocean energy. In India, wave energy is still experimental.

Conditions a good tidal site needs

• A large tidal range.
• A narrow inlet or funnel-shaped gulf where a dam can be built across the mouth.
• Enough trapped area behind the dam to hold a large volume of water.

Where it occurs

• Gulf of Khambhat (Cambay), Gujarat (west coast, Arabian Sea): a narrow, funnel-shaped gulf with a very large tidal range. It has India's highest tidal potential.
• Gulf of Kachchh, Gujarat (west coast): also funnel-shaped, with a very large tidal range.
• Sundarbans, Ganga delta, West Bengal (east coast): the main tidal site on the east coast, in a mangrove delta.
• Status in India: no large tidal plant has been built yet. Proposals have not turned into working plants. NCERT says the potential has "not yet been utilised".
• World: the Bay of Fundy (Canada) has the highest tides in the world. It is the textbook example of a huge tidal range in a funnel-shaped bay.

Don't confuse with

• Wave energy: this comes from the up-and-down motion of waves, which wind creates. Tidal energy comes from the rise and fall of tides, which the Moon and Sun create. Wave energy works on exposed coasts and is still experimental.
• Ocean thermal energy conversion (OTEC): OTEC uses the temperature difference of about 20°C between warm surface water and cold deep water. It needs no tide. India's pilot plant is at Kavaratti (Lakshadweep), run by NIOT [4][5].
• Hydroelectricity: this uses river water falling one way, from a reservoir on land. Tidal power uses seawater that moves in and out with the tide.
• Geothermal energy: this is the only one of these sources that is round-the-clock and weather-independent [2]. Tidal power is predictable, but it stops and starts with the tide cycle.

Prelims Hooks

• Best tidal sites in India: Gulf of Khambhat and Gulf of Kachchh (both in Gujarat, west coast) and the Sundarbans (West Bengal, Ganga delta, east coast).
• Why the Gujarat gulfs are best: they are narrow and funnel-shaped, so they have a very large tidal range.
• Status trap: no large tidal power plant works in India yet. Any option saying India has a working large tidal plant is wrong.
• Working principle (NCERT Class 10): a floodgate dam traps water at high tide. The water flows out through turbines as the tide falls.
• Matching sources to their drivers: tidal → tidal range (Moon and Sun); wave → wave motion (wind); OTEC → about 20°C temperature difference; geothermal → heat from inside the Earth.
• "Round-the-clock" trap: tidal power follows the tide cycle. Among these sources, only geothermal is round-the-clock and weather-independent [2].

Mains Points

• Physical geography decides where tidal energy is possible.
• Tidal potential is highest in the funnel-shaped gulfs of the west coast (Khambhat, Kachchh), because they have very large tidal ranges.
• The east coast has one major site, the Sundarbans in the Ganga delta.

• So tidal power is a site-specific resource, unlike solar power, which can be built in many places.

• Why the potential is still unused (GS-III):

• High cost: dams across wide gulfs are very expensive to build.
• Environmental harm: the dams change how water flows in and out. This can damage mangroves and mudflats, for example in the Sundarbans and the Gulf of Kachchh.

• Supply rises and falls: output follows the tide cycle, so the grid needs other sources to fill the gaps.

• Role in India's energy mix:

• Tidal power is renewable and its timing is predictable. This could help India's 500 GW non-fossil capacity target for 2030.
• Today, wind (about 58.5 GW in August 2026) [3] and solar carry the renewable push.
• Tidal and wave energy are still in the proposal or experimental stage. They can only grow if costs fall and the plants are designed to protect coastal wetlands.

Related concepts

• Wind energy
• Offshore wind energy
• Ocean thermal energy conversion
• Geothermal energy

Read more

• Wind, tidal, ocean and geothermal energy