Tidal Energy from the Ocean

Extracts energy from the kinetic energy of the earth-moon-sun system.

Variations in water level along coastlines can be used to drive turbines --> technology is the same as low-head hydro power

Vertical tides on US coast range from 2 feet in Florida to more than 18 feet in Maine

To enhance efficiency of turbines driven by tidal currents, it is desireable to build a damlike structure across the mouth of a tidal basin in order to direct the flow to a turbine

Turbines designed for work at both high and low tide (inflow or outflow)

Intermittent tidal flow is major problem. Tidal facility produces about 1/3 the electrical energy of a hydro facility of the same peak capacity

Two tidal plants in the world:

• 1 MW facility on the White Sea in Russia (1969)
• 240-MW on the Rance River, St. Malo France (1967) --> has 750 meter long dike to impound tides that can be as high as 13 meters (!)

Potential Sites in the US

• Alaska (Cook Inlet)
• Bay of Funday (US-Canadian Border; NE Coast of US) --> most favorable site in the World --> would produce about 30,000 MW in total (1/2 for the US)
• A 20 MW demonstration plant has been built here
• Locally (New England) this is a potential important source of power but on national scale is just a few percent of our (insatiable) need for power

Bottom Line: There aren't many favorable sites in the world for tidal power and the estimated capacity is 50 times smaller than the world's hydroelectric power capacity.

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