Turning the Tide; December 2008; Scientific American Earth 3.0; by Larry Greenemeier; 2 Page(s)

The earth¿s oceans, tugged by the moon and sun, ebb and flow over more than 70 percent of the planet. After fits and starts, researchers have developed a number of technologies to effectively harness some of that kinetic energy. Now a handful of entrepreneurs are trying to create a commercial market.

Underwater Windmills The most advanced demonstration operates at the bottom of New York City¿s East River, which is actually a tidal channel. In 2006 Verdant Power planted six windmill-like turbines on the riverbed, underneath 30 feet of water, away from boat traffic. Each turbine, 16 feet in diameter, churns at up to 32 revolutions per minute to transform strong tidal forces into electricity. Despite initial setbacks¿the river¿s potent flow damaged some of the rotors and snapped some of the original fiberglass and steel blades¿the company has kept two of the turbines operating, enough to attract $8.5 million in government funds for further development and testing.