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Tidal turbines off Marrowstone proceed toward permits November 9, 2009

25563aPlans are moving ahead to place a trio of underwater, tide-powered turbines on the sea floor one-third of a mile east of Marrowstone Island’s Nodule Point.

A briefing held Oct. 22 in Port Townsend for federal, state and local regulators revealed details of the pilot project, which is being managed by the U.S. Navy based on a direct multi-million-dollar appropriation inserted by a group of congressmen into the 2009 defense budget.

The trio of turbines, each resembling squat versions of Eastern Washington’s wind generators, would rise 36 feet up from the sea floor in 72 feet of water at a zero tide. The 4-ton turbines would be bolted to the three corners of a massive steel triangular platform that weighs some 40 tons.

Thanks to swift and consistent tidal ebbs and flows off east Marrowstone, the three uncovered blades on each unit would sweep through the seawater with a 16.4-foot diameter cycle at about 40 revolutions per minute – the tips moving 34 feet per second.

All three units are designed to swing 180 degrees when the tide shifts. The tidal current off Marrowstone is sufficient to power the turbines only for about six hours per day, according to reports.

Temporary project

The installation is designed to be a temporary pilot project to test the ability of the turbines to operate in a remote saltwater environment. The plan calls for the entire platform to be lifted from the sea floor within a year of installation. If permits and funding come through, the installation could happen over a three-week period in the early fall of 2011 or 2012.

Boaters would be warned away from the array by floating and lighted buoys that mark off a 1,300-foot by 1,300-foot surface area. Proponents say that in an existing experimental display of the underwater turbines in the East River off Manhattan in New York, fish tend to steer clear of the rotating turbines. However, an official said at the Oct. 22 briefing that it might be possible to brake the blades to a halt if marine mammals are detected in the area.

Power from the turbines would flow through a trio of cables to a junction box on the platform, and from there to a second junction box on the ocean floor about 140 feet beyond. From there, the steel-jacketed, 2-inch-diameter trunk cable would reach shore through a unique horizontal borehole that bypasses tidal zones and coastal zone disturbances.

The project, called the Navy Puget Sound Hydrokinetic Project (NPS-KHPS), is being managed by the Navy, thanks to the congressional appropriation that has already approved $2.4 million for what could be a $14 million total over five years, according to the Navy’s Mike McCallister, who led the briefing on Oct. 22. The Navy intends to bring the power ashore to Naval Magazine Indian Island.

Horizontal drilling
The power cable could come to Indian Island after coming ashore at an east Marrowstone park, and then be carried by overhead wires to the naval base with the cooperation of Puget Sound Energy. Or the cable could snake underwater for some four miles around the southern end of Marrowstone to the southern end of Indian Island near Oak Bay Park and come ashore directly. While discussion has taken place about the PSE option, no decisions have been made.

A unique technology called “horizontal directional drilling” is expected to minimize environmental impacts of bringing the power cable ashore. A borehole is drilled from the land that bends downward and then moves horizontally below the beach until it punches through into saltwater 60 to 90 feet below the intertidal zone. A flexible PVC pipe is placed in the borehole, and later the power cable is pulled through the pipe.

An on-shore vault is the landward anchor for the cable. When the power gets to Indian Island, a small monitoring station tracks the power, monitors the underwater location and controls the turbines.

The NPS-KHPS tidal generator proposal is a pilot project to demonstrate the underwater tidal technology in a remote saltwater environment. It is still in the preapplication phase under the National Environmental Protection Act, with the Navy as the lead agency.

Stacie Hoskins of the Jefferson County Department of Community Development, who attended the Oct. 22 briefing, said the county has no direct oversight over the project, as no county permits are needed. However the state Department of Ecology (DOE) is involved and is charged with ensuring that the project complies with county shorelines laws before issuing state permits.

Rebekah Padgett, federal permit manager with DOE, said her review would take county code into account. Other state and federal officials are looking at possible impacts on marine life, she said. Other key agencies are the U.S. Army Corps of Engineers and the Naval Facilities Engineering Command.

By Scott Wilson,The Leader – http://www.ptleader.com/main.asp?SectionID=36&SubSectionID=55&ArticleID=25563

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