To rein in the adverse effect of climate change, the world is embracing non-fossil fuel based energy for consumption. The prominent ones among them are solar energy, wind energy, hydroelectric energy and tidal energy. Among the renewable energies tidal energy is least explored but it has tremendous potential for future energy supply due to greater predictability.
The tidal cycle occurs every 12 hours due to the gravitational force of the moon. The difference in water height from low tide and high tide is potential energy. To capture sufficient power from the tidal energy potential, the height of high tide must be at least five meters (16 feet) greater than low tide. There are only approximately 20 locations on earth with tides this high and India is one of them. The Gulf of Cambay and the Gulf of Kutch in Gujarat on the west coast have the maximum tidal range of 11m and 8m with average tidal range of 6.77m and 5.23m respectively.
Oceanic tides are used to generate electricity by constructing floodgate dam across inlets of sea/ocean. During high tide water flows into the inlet and gets trapped when the gate is closed. After the tide falls outside the floodgate, the water retained by the floodgate flows back to the sea via a pipe that carries it through a power generating turbine.
Prominent tidal power stations of the world
• The first tidal power station of the world became operational in 1966, La Rance in France. It has an installed capacity of 240 MW and is also the second largest tidal plant in the world.
• Sihwa lake tidal power station in South Korea is the world largest tidal power station with installed capacity of 254 MW, came up in 2011.
• The first tidal power site in North America is the Annapolis Royal generating station, Nova Scotia, which opened in 1984 on an inlet of the Bay of Fundy. It has 20 MW installed capacity.
India’s potential and initiative
Total identified potential of Tidal Energy is about 9000 MW in West Coast Gulf of Cambay (7000 MW), Gulf of Kutch (1200 MW) and in East Coast the Ganges Delta in the Sunderbans in West Bengal for small scale tidal power development estimates the potential in this region to be about 100 MW.
In 2011, Government of Gujarat signed MOU for establishing a 250 MW tidal power project in Gulf of Kutch with GPCL, Atlantis Resource Corporation (U.K) and PMES, Singapore. A 50 MW tidal power project at Mandavi in kutchh district has been initiated in first phase.
The Ministry of New & Renewable Energy (MNRE) in 2008, sanctioned a demonstration project for setting up a 3.75 MW tidal power plant at Durgaduani Creek in Sunderbans, West Bengal but due to some reason it could not see the light of the day.
• Tides are totally predictable so energy availability duration can be predicted.
• It is completely carbon neutral
• Higher cost of installation and limited availability of sites.
• Inflexible power generation due to dependency on high tides.
• Environmental impact in local area due to flooding and landform modification.
Tidal power has traditionally suffered from relatively high cost and limited availability of sites with sufficiently high tidal ranges or flow velocities, thus constricting its total availability.
The sector has the potential to grow, fuelling economic growth, reduction of carbon footprint and creating jobs not only along the coasts but also inland along its supply chains. A variety of different technologies are currently under development throughout the world to harness this energy in all its forms including waves (40,000 MW), tides (9000 MW) and thermal gradients (180,000 MW).
Countries like United Kingdom, Russia, South Korea and Philippines are investing hugely in tidal projects and see it as a way of limiting their carbon footprint. India too has realized its potential and initiated tidal projects along its west coast. In the present circumstances, it holds a greater relevance as India has pledged to reduce its emission intensity by 33 to 35 percent compared to 2005 levels, by 2030 and 40 per cent of the total installed power capacity in 2030 would be based on non-fossil fuel based sources.