Manhattan tests underwater turbines


Resembling and working much like stout underwater windmills, the six 15-foot-tall turbines will draw energy from tidal currents to power a nearby supermarket and parking garage.

The company calls the project the first to use multiple underwater turbines to create usable power. Backers say the technology could ultimately provide a reliable, environmentally friendly and largely invisible solution to many global energy needs.

"It’s very, very green energy," said Dean Corren, the company’s director of technology development. "There’s a lot of energy in that flowing water. Our goal is to capture a small amount of that."

Traditional hydropower from dams, where water is trapped at a high level and released, provides about 7 percent of the nation’s electricity, but worries over damaging river environments and harming migrating fish have hindered new development.

The "hydro-kinetic" or "in-stream" technology works by submerging turbines into the natural path of moving water, such as a river, canal or deep ocean current.

"Fish and marine mammals can easily swim around," said George Hagerman, a Virginia Tech researcher who co-authored a study on in-stream energy issued this month. "It doesn’t have anywhere near the impact of a dam."

Learning lessons from the wind industry, where large windmill blades have killed birds, projects such as the East River experiment include extensive monitoring to ensure fish are not harmed.

The blunt rotor blades, spanning more than 16 feet tip to tip, will turn at a slow 32 rpm. Each turbine, anchored to bedrock and widely spaced in 30 feet of water, will work in both directions to accommodate reversing tidal currents.The technology is part of a growing effort to harness new forms of water energy, including using the motion of wind-driven ocean waves and "lunar power," the moon’s gravitational effect on tides, Hagerman said.

While firms in the United Kingdom are often leading the way, advocates of the technology see vast untapped potential in the U.S., with its extensive coastal waters and numerous rivers and waterways.

With rising fossil fuel prices, alternative energy has lately become big business. Wind power will likely produce enough electricity in the U.S. to run 2.3 million homes this year, according to the American Wind Energy Association.

Texas officials announced plans on May 12 to build the nation’s largest offshore wind farm in the Gulf of Mexico, with up to 170 windmills generating 500 megawatts of electricity – power for 125,000 homes.

In comparison, new forms of hydropower are just getting started.

Verdant’s 18-month test starting this summer should produce up to 200 kilowatts at peak capacity. If the test succeeds, the next stage in 2010 would use up to 300 improved turbines generating enough power for 8,000 New York homes.

With a commercial deployment three times larger than that, New York could earn the title of the city powered by the most locally produced renewable energy, said Trey Taylor, president of Verdant Power, which launched in 2000.

He said that while river turbines will likely never serve more than a tiny fraction of the city’s energy needs, the technology has advantages over other renewable sources.

"The wind doesn’t always blow and the sun doesn’t always shine," Taylor said, but the new forms of hydropower are very reliable, running day and night.

He said the submarine turbines also are out of sight, avoiding conflicts like the one in Cape Cod, Massachusetts, where residents oppose a proposed wind farm, saying it would spoil scenic views.

The river power also is produced locally, adding security and savings by replacing electricity transmitted from distant power plants, Taylor said.

With interest from the Brazilian government, the company has a team scouting locations in the Amazon basin, where river turbines could replace diesel generators used in about 1,000 villages. The company has another project in Canada and plans to deploy turbines in man-made canals and aqueducts in California.

For now the more modest action is on Roosevelt Island, where Verdant Power’s control room by the East River is a metal cargo container stuffed with electronics. It is about 20 feet from the Gristedes supermarket’s deli section, soon to be chilled for free with river power.

The company had to overcome a series of delays and federal and local government hurdles. Taylor said his company chose New York in part because its tough regulatory environment would be a "learning process."

Corren predicted new hydropower will grow like wind power, while avoiding that industry’s mistakes.

"There’s no such thing as a 100 percent clean source of energy," he said, "but this is as close as you can get."

On the Web:

Web video: —RIVER—TURBINES—ADV21—COX.html

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