A bay that charges the batteries

Published online: Sep 15, 2010 News Soundings Online

Down East Maine's enormous tidal range - a bane to mariners - one day could be a boon to the region as a renewable source of electrical energy.

A 60-kW turbine suspended 20 feet under Maine's Cobscook Bay is producing electricity to recharge a bank of batteries that supplies power to a 41-foot utility boat at the Coast Guard station in nearby Eastport.

The 13-ton turbine, which looks like a paddle wheel, is in a rectangular frame 14 feet wide, 14 feet deep and 46 feet long. Called a cross-flow turbine, its composite blades - actually carefully sculpted foils - spin in the tidal current, which flows at a speed of up to 6 knots four times a day during the 18- to 20-foot tidal changes typical of the waters flowing into and out of the Bay of Fundy.

The turbine drives a fixed-magnet generator, which powers the unit's monitoring systems and recharges the battery bank - eight 12-volt batteries stored on a 20-foot skiff tied to the turbine's 60-foot barge, Energy Tide 2. Once the batteries are recharged, the skiff is towed to the Coast Guard station and swapped out for a second skiff loaded with batteries, which goes back to the barge for recharging.

Ocean Renewable Power Co. switched on the power for the Coast Guard Aug. 18.

The battery banks supply electricity to the 41-footer's heater, its battery charger, radio chargers and other systems while it is dockside, says Capt. Jim McPherson, commander of Coast Guard Sector Northern New England.

Because Ocean Renewable Power already planned to test the tidal generator in Cobscook Bay, the Coast Guard awarded the company a $100,000 grant to put it to work supplying electricity to its station. When linked to an inverter, the battery banks supply one-third to one-half of the daily shoreside power needs of the 41-footer, says John Ferland, vice president of project development for the power company.

McPherson hopes to take alternative energy to other Coast Guard stations in Maine. "We hope to have a station one day that's completely off the grid," he says. "Zero consumption."

Read more in the November issue of Soundings magazine.

http://www.soundingsonline.com/news/dispatches/582-sept-15-2010/265552-going-with-the-flow-powers-coast-guard-boat

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