Tidal power or tidal energy is energy (potential or kinetic) obtained from sea tides which is converted into a useful form of power, mainly electricity. Tidal energy has huge potential in future for electricity generation, though not widely used as of date. The behaviour of tides is definitely predictable but that of wind energy and solar power is not. As tidal energy is a consistent source of kinetic energy caused by regular tide cycles influenced by the phases of the moon which are definite and known.
Tide mills which (to mill the grains) used this mechanical power of waves were in use earlier both in Europe and Atlantic coast of North America. The world’s first large-scale tidal power plant is the Rance Tidal Power Station in France, which became operational in 1966. Tidal turbines in simple words can be called as underwater windmills though are not exactly same. Tidal turbine rotors are much smaller in size as compared to windmills as sea water is 832 times denser than air, hence the installations of these can be comparatively in smaller space. But the tidal turbine and its components design and maintenance has always been a challenge. Also, the salty water plays a major role during design consideration.
There are four methods of converting the tidal power into electricity –
Tidal Stream turbine generators: – Tidal turbines in simple words can be called as underwater windmills though are not exactly same. Tidal turbines are installed on the seabed at locations where strong and continuous ocean currents are available. The submerged rotors of these turbines make use of the kinetic energy of marine currents to drive generators to produce electricity. The tidal energy is bidirectional and hence the turbine rotor design has to be adapted accordingly.
Tidal Barrage – it uses the potential energy in the difference in height between high and low tides. The potential energy from a tide is seized with the help of specialized dams; it is then converted into mechanical energy to drive turbines that generate electrical power through generators.
Dynamic Tidal Power (DTP) – It involves a construction of very long dams ranging from 30 to 50 kilometers from coasts running deep in the ocean and make use of both potential and kinetic energy of the tides.
Tidal Lagoon – this is a newer technology, involving a construction of circular retaining walls (not so deep in the ocean) embedded with turbines to capture potential energy of tides. It is a similar concept to tidal barrage but the locations are artificial.
French energy company ENGIE is going a big way in “exploring this limitless energy potential” and plans to build tidal energy project on the western coast of the Cotentin peninsula in the English Channel. Also in Gujarat Indian government is setting up a 50 MW plant at the Gulf of Kutch.