Tidal EnergyExplained By

Kavan Oza (IU1241060031)Maharshi Pandya(IU1241060034)

Ashir Sheth(IU1241060053)

Outlines

How Tides Occurs?Introduction of Tidal Energy How to Generate Tidal EnergyTypes of Tidal Power PlantTidal Scenario In IndiaAdvantages – Dis advantages

Tidal Energy

Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into

useful forms of power, mainly electricity.

Why Tides Occur?Tidal forces are periodic variations in gravitational

attraction exerted by moon. These forces create corresponding motions or

currents in the world's oceans. Due to the strong attraction to the oceans, a

bulge in the water level is created, causing a temporary increase in sea level.

 When the sea level is raised, water from the middle of the ocean is forced to move toward the shorelines, creating a tide.

This occurrence takes place in an unfailing manner, due to the consistent pattern of the moon’s orbit around the earth. 

How To Generate Tidal Energy??Tidal stream generators (or TSGs) make use of the kinetic energy of moving water to power turbines, in a similar way to wind turbines that use wind to power turbines.Some tidal generators can be built into the structures of existing bridges, involving virtuallyno aesthetic problems.Land constrictions such as straits or inlets can create high velocities at specific sites, which can be captured with the use of turbines.

This form of generation has many advantages over its other tidal energy rivals. The turbines are submerged in the water and are therefore out of sight. They don’t pose a problem for navigation and shipping and require the use of much less material in construction. They function best in areas where the water velocity is 2 - 2.5 m/s

Tidal barrages make use of the potential energy in the difference in height between high and low tides. When using tidal barrages to generate power, the potential energy from a is seized through strategic placement of specialized dams. When the sea level rises and the tide begins to come in, the temporary increase in tidal power is channeled into a large basin behind the dam, holding a large amount of potential energy. With the receding tide, this energy is then converted into

mechanical energy as the water is released through large turbines that create electrical power through the use of generators.

The power available from the turbine at any particular instant is given by:

Where,Cd = Discharge CoefficientA = Cross sectional area (m2)G = gravity = 9.81r = density (kg/m3)

The discharge coefficient accounts forthe restrictive effect of the flow passage within the barrage on the passing water.

The equation above illustrates how important the difference between the water levels of the sea and the basin, (Z1-Z2),

is when calculating the power produced.

Tidal range may vary over a wide range (4.5-12.4 m) from site to site. A tidal range of at least 7 m is required for economical operation and for sufficient head of water for the turbines.

A major drawback of tidal power stations is that they can only generate when the tide is flowing in or out - in other words, only for 10 hours each day.

However, tides are totally predictable, so we can plan to have other power stations generating at those times when the tidal station is out of action.

This is a 240 megawatt (1 megawatt = 1 MW = 1 million watts) at the mouth of the La Rance river estuary on the northern coast of France (a large coal or nuclear power plant generates about 1,000 MW of electricity). The La Rance generating station has been in operation since 1966 and has been a very reliable source of electricity for France. It is the only one in Europe but there Is a possibility that 10% of UK’s Electricity demand can be satisfied byTidal energy..

The technology required for tidal power is well developed, and the main barrier to increased use of the tides is that of construction costs.

There is a high capital cost for a tidal energy project, with possibly a 10-year construction period.

Therefore, the electricity cost is very sensitive to the discount rate.The major factors in determining the cost effectiveness of a tidal

power site are the size (length and height) of the barrage required, and the difference in height between high and low tide.

These factors can be expressed in what is called a site’s “Gibrat”

ratio. The Gibrat ratio is the ratio of the length of the barrage in metres to the annual energy production in kilowatt hours (1 kilowatt hour = 1 KWH = 1000 watts used for 1 hour).

The smaller the Gibrat site ratio, the more desireable the site. 

Indian Tidal Energy Scenario

Tidal Energy is one of the new and emerging technologies, which is commercially not viable and still in Research & Development (R&D) stage. India has a long coastline with the estuaries and gulfs where tides are strong enough to move turbines for electrical power generation.

Tidal Energy Potential

As per the studies, the Gulf of Kutch and Gulf of Cambay in Gujarat and Sunderbans area in West Bengal are the only potential sites in India for the development of Tidal Energy Projects.

Central Electricity Authority (CEA) undertook a study for the assessment of tidal energy potential in India. According to the study, the identified economic power potential is of the order of 8000 MW

Region State Tidal Potential (MW)

Gulf of Cambay (Khambhat)

Gujarat 7000

Gulf of Kutch Gujarat 1200

Gangatic Delta, Sunderbans

West Benga 100

In February 2008, under the Tidal Energy Programme, the Ministry of New & Renewable Energy (MNRE) sanctioned a demonstration project for setting up a 3.75 MW tidal power plant at Durgaduani Creek in Sunderbans, West Bengal.

The NHPC Limited was given responsibility to execute the project. The total estimated project cost was INR 48 crores, out of which 90% (INR 43.20 crores) was to be shared by the MNRE and the remaining 10% (INR 4.80 crores) by the Government of West Bengal.

However, the project has been discontinued due to very high tender cost amounting to INR 238 crores against originally estimated cost of INR 48 crores.

Tidal Power Projects in Gulf of Kutch,

A committee was constituted under the Central Electricity Authority (CEA) on the 900 MW Kutch Tidal Power Project for estimating the cost of the project. A techno-economic feasibility study was carried out by the CEA in 1988 for a 900 MW Tidal Power Project. A revised estimate of INR 6184 crores was worked out for the execution of this project in 1993.

Mandavi Tidal Power Project (250 MW) in Kutch

In January 2011, Government of Gujarat signed a Memorandum of Understanding (MoU) for establishing a 250 MW tidal power project in Gulf of Kutch with Gujarat Power Corporation Ltd. (GPCL) Vadodara, Atlantis Resource Corporation, United Kingdom and Perfect Mining Energy Solutions (PMES), Singapore.

A Special Purpose Vehicle was incorporated in May, 2011 and GPCL has taken up a 50 MW tidal power project at Mandavi in district Kutch in the first phase.

As part of the agreed upon terms of the MoU for a total of 250MW of future tidal power development, the initial 50MW project could be scaled up to more than 200MW of installed capacity. The project is expected to cost around Rs 750 crore 

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