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Coast Guard turns to tidal power

The Old Sow whirlpool in Maine may help supply electricity to its Eastport station

A sight to behold and a hazard to avoid in a small boat, Old Sow — one of the world’s largest tidal whirlpools — is fueled by a 22-foot tidal change the Coast Guard hopes to harness to generate electricity for its Eastport, Maine, station.

The Coast Guard hopes to harness the powerful whirlpool using a tidal generator.

“Every day we have the wind and the current and the tides up here,” says Capt. James McPherson, commander of Sector Northern New England. What better place than the coast of Maine to tap alternative energy sources? he asks. The tidal currents run 6 knots four times a day like clockwork off Eastport, and the Department of Energy ranks the winds there excellent to outstanding.

Since the Coast Guard pays for electricity just like everyone else, it is always looking for ways to trim its utility bills, McPherson says. “We know that energy costs continue to rise,” he says. “We’re just trying to be responsible.”

On Earth Day, April 22, the Coast Guard announced it is offering a $100,000 grant to a qualified partner to test “in-stream” tidal generators to supply electricity for some non-critical functions — battery recharges, household lighting, portable electric heaters and pier lights, for instance — at its Eastport station. McPherson expects to have a tidal generator in the water by summer’s end. If it works out, other search-and-rescue stations in the Coast Guard sector covering Maine, New Hampshire and Vermont could benefit as well, he says.

McPherson’s unit already has wind generators producing electricity to power non-essential computers, monitors and servers at stations in South Portland and Southwest Harbor, Maine. The 365 kilowatt hours of electricity those generators produce saves the sector $200 a month on its electric bill at Southwest Harbor alone, he says. The wind generators cost $6,000 to buy and install. “That’s going to pay for itself in a few years,” he says.

The Coast Guard powers 90 percent of its lighted navigation buoys and 60 of 68 lighthouses with solar panels. “This is just a continuation of that,” he says.

Old Sow, the largest tidal whirlpool in the Western Hemisphere, displays the raw power of the tidal currents that run along the coast between Passamaquoddy Bay and the Bay of Fundy. Measuring 250 feet across, the Sow’s waters churn and swirl and make strange sow-like or sucking noises over an expanse of eddies and troughs and holes and gyres — or at times one large funnel — where a 20-foot-plus tide sweeps past both sides of Deer Island northeast of Eastport. At Deer’s southern tip, the waters turn sharply into or out of the Western Passage, which funnels the tidal flow and takes it over a bottom that rises and falls precipitously to depths of 400 feet, 119 feet, then 350 feet again.

“Old Sow generally creates tremendous water turbulence locally, but it does not usually constitute a navigation hazard for larger vessels; small craft are warned to avoid these waters when the tide is running,” the National Oceanic and Atmospheric Administration warns in a publication on local currents.

“We know the tides are strong,” McPherson says. “We’re in them every day.”

Early in April, Ocean Renewable Power Co., an ocean-technology firm that has been testing a prototype tidal generator in the Western Passage and nearby Cobscook Bay since December 2007, received a $951,500 federal grant to continue its work there. Over a year’s time, the company tested a one-third-scale tidal generator at both sites, says John Ferland, Ocean Renewable’s northeast project director. “We’ve proven the concept,” he says.

The grant enables Ocean Renewable and partners — the University of Maine, Maine Maritime Academy and the University of Massachusetts at Dartmouth — to continue the testing and refine the turbine technology. Ocean Renewable’s deep-water generator is a sophisticated paddlewheel-type unit, modular in design — each module 86 feet long and 14 feet high and capable of generating 250 kilowatts. Ferland plans to stack the generators four high to create a 1-megawatt station and fix the generator to the bottom at a depth of 60 feet. “We shouldn’t be a navigation hazard at all,” he says.

The unit should be able to power 350 homes. Ferland plans to have a pilot 1-megawatt station operating in Western Passage or Cobscook Bay by 2010.

The Coast Guard project will test the feasibility of using tidal power to augment the electric power supply at the Eastport station, says Capt. Matthew Sisson, commanding officer of the Coast Guard’s Research and Development Center in New London, Conn. If tidal power works well there, the R&D center will look at how it might be used at other stations and in other regions — possibly Alaska and the Pacific Northwest, where there are big tidal changes or other fast-running water. Coast Guard stations are uniquely located on the coast, where wind and water are always potential alternative energy sources, he says.

The pilot tidal generation project is part of a larger Coast Guard effort to use alternative energy. In Mobile, Ala., it is running water through pipes 15 feet underground, where the temperature is a constant 55 F, to help heat and cool a 95,000-square-foot aviation hangar.

Sisson says this geothermal assist generates big cost savings. The R&D center’s own offices were designed with energy savings in mind, and Sisson says he plans to cut utility costs even more with a wind generator. Taking its effort a step further, the Coast Guard plans to host an Alternative Energy Summit for industry and government this summer following GovEnergy 2009, an Aug. 9-12 energy savings expo in Providence, R.I. The Coast Guard also will host an offshoot of World Maritime Day Oct. 16 in New York City. The event highlights developments in green vessels and equipment.

Sisson says the Coast Guard has been in the business of figuring out how to power remote boat stations and lighthouses with alternative energy since its earliest days, and is returning now to those roots. “It’s in our DNA,” he says.

This article originally appeared in the August 2009 issue.