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power & industrial
HYDROPOWER
East River's Strong Tides Power Submerged Turbines
By William J. Angelo
 

A section of New York’s East River is now the test bed for a tide-powered turbine farm that could cost $20 million and generate up to 10 MW of electricity when completed in 2007. The project is a global first and could lead to a new, stable and nonpolluting energy source.

Out of Sight. Low-rpm turbines will generate power without harming
marine life.

After testing a single 16-kW barge-mounted turbine on the river for six weeks in 2003, Verdant Power LLC, Arlington, Va., is now installing the first two of six proprietary underwater turbines for an 18-month test that could green-light a federal license for the proposed project. The tide-powered farm would consist of up to 300 turbines stretched along a mile-long, 270-ft wide section on the east side of Roosevelt Island, where the current runs at a steady 4 knots. "The power from the test will go to two specific customers on the island, a grocery store and a parking deck," says Dean R. Corren, Verdant director of technology development. "This will help reduce their draw on the grid."

The 16-ft-long unducted axial flow turbines are bolted to rock-socketed, grout-filled steel pipe piles at an operating depth of about 8 ft below the surface of the 30-ft to 40-ft deep river. The units will operate in a bi-directional mode, taking advantage of the river’s ebb and flow. Each turbine has three slow-turning composite blades to form a rotor 16-ft in diameter. Because the blades turn at a leisurely 36 rpm, engineers did not feel a need to design cages to protect aquatic life or to fend off river debris.

The turbines can convert kinetic hydro energy into power ranging from 25 kW to 250 kW, depending on turbine size and current. Verdant plans on using 36-kW units in the East River. Kinetic energy is converted to mechanical power in a nacelle within the turbine. Cables bring power to shore and tie it into the grid at a Roosevelt Island substation.

"There is a similar unit offshore in the U.K. but this is a global first to place a field of turbines producing distributed electricity," says Trey Taylor, Verdant president. The prototype turbines are being assembled by Zak Inc, Troy, N.Y., and installed by locally based MVN Associates.

TAYLOR

Halfway through the performance test company and state officials should have enough information to decide if the project is feasible. "Nine months out we’ll file for a Federal Energy Regulatory Commission license," says Taylor. "Once we get the license we will start the build-out, which will take about a year to complete. We still need to work out fish migration, security and navigation issues."

Taylor notes that tide-powered, or in-stream, kinetic hydro turbines are more advantageous than wind or solar powered turbines because placement can be made anywhere there is predictable natural or man-made water flow. “More could be built in tidal estuaries and in rivers near cities and in man-made channels such as irrigation canals that could help meet our energy needs,” he says.
Verdant is also working on a scaled-down turbine for use in California irrigation canals. The firm has contacted several irrigation districts and is looking for a partner to start a pilot project. “It could use three-ft rotors on 10-kW units,” says Taylor. “There are 11,000 miles of canals and aqueducts in California and we’re investigating speed, depth and accessibility.”

The East River surface testing cost about $1.5 million, one-third of which was partially underwritten by the New York State Energy Research and Development Authority. NYSERDA is Verdant’s research partner in New York and will help with the "six pack" test funding by contributing another $500,000. "We’re looking at all different sources of renewable energy for state needs," says Joseph H. Sayer, NYSERDA senior project manager. "Tide-powered turbines seem not to have a major environmental impact, are quiet with no visibility impairment and New York City is an energy load center in need of new generation, so this could help."

Sayer notes New York state is estimated to have 1,000 MW of potential in-stream kinetic hydropower available. "Hopefully developers will be inclined to work at other sites besides the East River," he says.

(Images courtesy of Verdnat Power, LLC)

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