Tidal Energy

Tidal Energy - predictable and powerful

Tidal energy or tidal power, is the energy from the tides caused by the gravitational pull of the moon and sun, and the rotation of the earth. Near shore, water levels can vary up to 40 feet. Only about 20 locations on the earth have good inlets and a large enough tidal range (vertical difference between the highest high tide and the lowest low tide) -- about ten feet -- to produce energy economically.  Like solar energy, tidal energy is considered a renewable source of energy.  Wave energy and wave power are based on similar uses of the tides and constant ocean energy.

What is tidal energy?

How is tidal energy harnessed?

The simplest generation system for tidal plants involves a dam, known as a barrage, across an inlet. Sluice gates on the barrage allow the tidal basin to fill on the incoming high tides and to empty through the turbine system on the outgoing tide, also know as the ebb tide. There are two-way systems that generate electricity on both the incoming and outgoing tides. Tidal power generated in this way is analogous to hydroelectric power generation, but with the water source fluctuating on a daily basis.

What is the advantage of tidal energy barrages?

Tides are totally predictable, so plans can easily be made to have other power stations generating at times when the tidal energy barrage is out of action.

Are there disadvantages to tidal energy barrages?

A major drawback of tidal power stations is that they can only generate when the tide is flowing in or out -- ten hours each day. Tidal energy barrages can change the tidal level in the basin and increase turbidity in the water (which can have long term environmental effects). There aren’t very many viable sites in the world. Infrastructure costs are high. Tidal energy barrages can also affect navigation and recreation and have a negative impact on plants and animals in the estuaries.

Where are some tidal energy barrages located?

There are currently only two commercial-sized barrages in operation in the world. One is located in the Rance estuary in northern France, which has been operating since 1966. The other is in the Bay of Fundy, Nova Scotia, Canada. This site opened in 1984. The U.S. has no tidal plants and only a few sites where tidal energy could be produced economically.

How do tidal turbines work?

Tidal turbines are a relatively new technology that draws energy from currents in much the same way as wind turbines do. Tidal turbines can be located anywhere there is strong tidal flow. Because water is about 800 times denser than air, tidal turbines will have to be much sturdier than wind turbines.

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