KEYSTONE — The latest news on the prospects for tides being used to generate power for Snohomish and Island counties: Good.
Early estimates for the speed of currents in Admiralty Inlet off Whidbey Island were 4 to 6 knots per hour.
New data shows it’s closer to 7 knots, potentially increasing the energy output of tidal turbines in the water.
The information was part of a host of data about Admiralty Inlet gathered recently by University of Washington researchers working with the Snohomish County PUD on its planned tidal power pilot project.
The PUD estimates it could have one to three turbines in the water near Fort Casey State Park by 2011. Three turbines — which each weigh 400 tons apiece — could power up to 1,000 homes. Four other sites are still on the table as well. The number of turbines that would eventually go into the water has yet to be determined.
The U.S. Navy is planning a tidal installation of its own, off nearby Marrowstone Island near Port Townsend, which could be installed in 2010, officials have said.
Before putting any turbines in the water, the PUD needs to know the conditions in the area to make sure it’s suitable, officials said. They also need information to compare with conditions after the turbines are in the water, officials said.
Since April, UW researchers have been lowering and raising several types of gadgets in the water, roughly 200 feet deep, to get the lay of the land and sea.
They’ve come up with information on currents, water quality, noise, habitat and surface conditions. The work is far from done, however, and will continue off and on for another year.
The seabed is level and “cobbled” with small rocks, said Brian Polagye, a research assistant professor in the UW department of mechanical engineering. This means it’s a suitable surface for the turbines, as opposed to a ridge, a canyon or an area with rolling boulders, as is the case in the Bay of Fundy in Nova Scotia, Canada, he said.
The PUD plans to use turbines from OpenHydro, an Irish company that built turbines being used in a pilot project in Scotland — one of only five tidal power projects in the world, Polagye said.
A 400-ton turbine doesn’t have to be installed on the bottom, said Craig Collar, PUD senior manager of resource development.
“It is lowered down to the seabed and there it sits,” he said.
Each turbine sits about 20 meters up on a triangular platform whose dimensions are about 30 by 26 meters.
The turbines themselves are 10 meters wide and rotate only 10 to 15 times a minute. They don’t have exposed blade tips, two qualities that should minimize the effect on marine life, officials said. The turbines don’t have a price tag yet but are being designed to minimize maintenance.
Noise needs to be measured for the turbines’ potential effect on wildlife, especially marine mammals but other species as well, Polagye said.
Admiralty Inlet is part of the only route from the Pacific Ocean to Puget Sound and is therefore a busy shipping lane. The noise-measuring device has been picking up sound from the Port Townsend-Keystone ferry, other ships and from rocks as well.
“Trying to unwrap all that into a cohesive picture is what we’re going to spend the better part of the next year working on,” Polagye said.
The PUD has received $2.1 million in federal grants to pay for the research. They’re working with the UW’s Northwest National Marine Renewable Energy Center, which has received federal grant money of its own to do research on tidal projects.
It’s too early to tell if the encouraging news on the currents will have an effect on how many turbines the PUD puts in the water, spokesman Neil Neroutsos said.
“It’s encouraging, it’s good news,” he said.
Bill Sheets: 425-339-3439, sheets@heraldnet.com.
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