Tidal Power

Some of the oldest forms of energy generation use tidal power.  Tide Mills in Europe has been used for nearly 1,000 years mainly used for grinding grains. Tides are caused by the moon’s gravitational pull.  Tide power is considered an inexhaustible resource making it a renewable energy source.  In most cases electricity would not be generated 24 hours a day.  A conventional design would produce electricity for 6 to 12 hours in every 24 hour period. 

For Tidal Power to be effective to generate electricity there needs to be at least 16 feet between high and low tide.  There are only 40 places on earth with tidal ranges of this size.  Currently there are no tidal power plants in the U.S. but conditions in the Pacific Northwest and Atlantic Northeast are in place for tidal power generation.

Conventional Tidal Power technologies include the use of dams which create tidal lagoons.  Barrage traps water in a lagoon and when the level of water on the other side of the dam falls enough water is released turning turbines which generate electricity.  The largest installation of a tidal dam has been working on the Rance River in France since 1967 producing 600 million kWh annually.  

Tidal fences look like turnstiles which turn from the kinetic energy generated from the movement of tidal water.  Some currents along coastlines run 5 to 9 miles per hour which will generate electricity more efficiently than a wind turbine. 

Tidal turbines look similar to wind turbines but they are placed underwater.  They are arranged in rows adding multiple rows would large tidal turbine farms.  They function best when the water is moving at 4 to 6 miles per hour.  A tidal turbine is more efficient than its cousin the wind turbine generating as much electricity as a wind turbine four times its size. 

While tidal lagoons and tidal fences may disturb sea life migration Tidal turbines seem to be the most environmentally friendly because they do not block migratory paths.  The rotors on a tidal turbine turn slowly at 10 to 20 rpm.  The risk of sea life coming in contact with the rotor blades is extremely low.

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