Undersea turbines harness tides - Boat U.S. Reports

While producing electricity from offshore wind turbines is proving controversial in the United States (see BoatU.S. Magazine, September 2002), what about generating juice under the sea -- out of sight and out of mind? That's the approach taken in a small town on the northern tip of Norway where a turbine on the nearby Arctic seafloor generates electricity from tidal currents.

The 200-ton seabed turbine works by exploiting the natural rise and fall of the seas as the moon and sun cause a gravitational pull on the spinning Earth's oceans. As the tides ebb and flow, the turbine changes direction to face the oncoming current. And although the sub-sea turbine can only generate enough electricity for about 1,000 households in Hammerfest, it is deemed "friendlier" than other types of turbines -- it's silent, does not harm fish and other marine life and doesn't pose a hazard to navigation.

Though now working at a low capacity, the turbine will be upgraded over the next few years for a total cost of about $13 million. Tidal power plants, which trap water at high tides, and use the gravitational pull of the outgoing tide to generate electricity, seem the most popular method of harnessing the oceans' powerful energy. The only one in North America is in Nova Scotia where it uses the Bay of Fundy which has the world's highest tides at 39 feet.