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Some of the oldest ocean energy technologies use tidal power. Tides are 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 due to tides. Tidal power is more predictable than wind energy and solar power. A large enough tidal range 10 feet is needed to produce tidal energy economically. The United States has no tidal plants and only a few sites where tidal energy could be produced economically. France, England, Canada, and Russia have much more potential to use this type of energy, beecause seawater is much denser than air, ocean currents carry more energy than air currents. For example, a 15 meter (49.2 feet) tidal turbine can generate as much energy as a 60 metre (197 feet) diameter wind turbine. |
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