Tides are caused through a combination of forces created by the gravitational pull of the sun and the moon and the rotation of the earth. Energy naturally present in water bodies – or in their movement – can be used for generation of electricity, through tidal, wave and thermal energy. Energy can be extracted from tides in an environment friendly manner by creating a reservoir or basin behind a barrage and then passing tidal waters through turbines in the barrage to generate electricity.

Tidal energy is extremely site specific and requires mean tidal differences greater than 4 meters. It also requires favorable topographical conditions, such as estuaries or certain types of bays in order to bring down cost of dams, etc. Tidal energy is a clean mechanism and does not involve the use of fossil fuels. However, environmental concerns exist mainly due to higher silt formation at the shore (due to preventing tides from reaching the shore and washing away silt) and disruption to marine life near the tidal basin. Wave energy projects have lesser ecological impact than tidal wave energy projects. In terms of reliability, tidal energy projects are believed to be more predictable than those harnessing solar or wind energy, as occurrences of tides are fully predictable.

Since India is surrounded by sea on three sides, GoI has recognized its potential to harness tidal energy and MNRE has a full-fledged program on development of ocean/tidal energy for power generation.

France is currently the only country that has significantly harnessed tidal energy and has the largest tidal power station in the world. Built in 1966, the La Rance tidal power station of Electricite de France (EdF) in Mont Saint Michel (northern France) has a generating capacity of 240 MW. It has 24 bulb-type turbines, each of 10 MW rating.

The Severn Barrage is a proposed tidal power station to be built across the Bristol Channel (Severn Estuary) in the UK. The River Severn has a tidal range of 14m, making it perfect for tidal power generation. The Severn Barrage would involve the construction of a 16 km long barrage between Lavernock Point (Wales) and Brean Down (England). A total of 214 turbines, each of 40 MW, would be built into the barrage making it a colossal power plant of 8,560 MW of installed capacity with an average annual generation of 17 Gwh.

As discussed above – India as a result of being surrounded by sea on three sides, has a high potential to harness tidal energy. The three most potential locations in this regard are Gulf of Cambay (west coast), Gulf of Kutch (west coast) and Ganges Delta, Sundarbans, West Bengal (East Coast). The most attractive locations are the Gulf of Cambay and the Gulf of Kutch where the maximum tidal range is 11 m and 8 m with average tidal range of 6.77 m and 5.23 m, respectively. The Ganges Delta also has good locations for small scale tidal power development. The maximum tidal range in Sundarbans is approximately 5 m with an average tidal range of 2.97 m.

The identified economic tidal power potential in India is to the order of 8,000-9,000 MW with about 7,000 MW in the Gulf of Cambay, about 1,200 MW in the Gulf of Kutch and less than 100 MW in Sundarbans. The Kutch Tidal Power Project – with an installed capacity of about 900 MW -is estimated to cost about INR 1,460 crore generating electricity at about 90 paise per unit. The techno-economic feasibility report is now being examined.

The West Bengal Renewable Energy Development Authority (WBREDA) has authorized NHPC Ltd. to prepare a detailed project report on Durghadhauni Mini Tidal Energy plant with a capacity of 3.65 MW installed in the Sunderbans. The plant, which was developed by a joint collaboration between Indian Institute of Technology (IIT), Madras and National Institute of Ocean Technology (NIOT), Tamil Nadu – is providing electricity to nearly 15,000 homes.

Also Read about Advantages and Disadvantages of Tidal Energy.

Tidal Power Plants in India

The Indian tidal energy sector is attracting overseas companies as well. Atlantis Resources, a UK based tidal energy company, has secured a significant contract in an effort to utilize the power of the sea around India for the first time. The company has signed a deal with western state of Gujarat, in order to establish the feasibility of developing tidal power projects that are capable of generating more than 100 MW of power — enough to supply about 40,000 households.

 Organizations Working on Ocean/Tidal Energy in India

Source: Tidal Directory

i) Tidal Electricity – Like other forms of Energy, the main usage of Tidal Energy is in the generation of Electricity. Tidal Energy is being used in France to generate 240 MW of Tidal Electricity at very low costs. There are other smaller plants in operation in Canada, China and Korea as well. DOE has located 40 places in the world where the differences between the low and high tides is big enough to generate commercial levels of Tidal Electricity. Note the Power generated from Tidal Energy is reliable as Tides are uniform and predictable in nature.

ii) Grain Mills – Tidal Energy has been used for hundreds of years. Just like Wind Mills, Tidal Energy was used for the mechanical crushing of grains in Grain Mills. The movement of Turbines due to Tidal Energy was used in the crush Grains. However with the advents of Fossil Fuels,this usage of Tidal Energy has become quite low.

iii) Energy Storage – Tidal Energy can also be used as a store of Energy. Like many of the hydroelectric dams which can be used a large Energy Storage, so Tidal Barrages with their reservoirs can be modified to store energy. Though this has not been tried out, with suitable modifications Tidal Energy can be stored as well though costs may prove to be high.

The biggest and main use of Tidal Energy is in generation of Electricity and most of the research is being done towards this end. Tidal Electricity is cheap, long lived and non-polluting in nature. It has benefits over solar and wind power in the sense that it is predictable in nature and also has a higher load factor. The other usage of Tidal Energy are pretty low compared to Geothermal Energy which is primarily used for Heating Purposes.

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