‘Energetic site’ chosen for PUD’s tidal power test

With fast currents and little life, a small area about 180 feet below the water near the Keystone Ferry Terminal in Admiralty Inlet could be a tidal energy sweet spot.

“It’s a boring, dark, rocky bottom,” said Jim Thomson, an oceanographer with the University of Washington’s Applied Physics Lab. “That’s good.”

The area could become a field of three electricity-producing tidal turbines by 2011, said officials with the Snohomish County Public Utility District, which announced Tuesday that the demonstration turbines would be designed, built and installed by an Irish company.

Finding the ideal location has taken time.

After starting the search in a wide swath of open water between Whidbey Island and the Olympic Peninsula, researchers are now narrowing in on a roughly one-square-kilometer area near the ferry terminal. The spot has fast water, a flat sea-bottom and few fish.

A UW research vessel spent last week probing the area with high-tech equipment, including a robotic underwater camera. The group collected data about water speed, depth and marine populations.

At the narrow passage, currents rush into and out of Puget Sound at speeds of about 6 mph, considerably faster than a human can swim. Once every 12 hours, a slack tide slows the water for about 10 minutes. Otherwise, the tides are always rushing, officials said.

The strong current meant hard survey work, but “good energy,” said Brian Polagye, a UW researcher. “It is a very energetic site.”

Researchers will spend the rest of the year revisiting the site and crunching numbers as part of a $100,000 effort funded by the Department of Energy.

At maximum capacity, the three turbines could power roughly 700 homes, according to the PUD.

The 10-meter-wide turbine design selected by the PUD rotates just 10 times a minute and doesn’t have exposed blade tips, two qualities that should minimize impact on marine life, officials said. The turbines don’t have a price tag yet but are being designed to minimize maintenance.

Meanwhile, the U.S. Navy is planning a tidal installation of its own, off nearby Marrowstone Island, which could be installed in 2010, officials have said.

When the PUD’s final site is selected, it plans to install at least one specially-built turbine built by OpenHydro, an Irish company that has installed some tidal turbines off the coast of Scotland.

A special catamaran-style barge could be used to lower the turbine onto the flat bottom of Admiralty Inlet. Installation won’t require any pilings, pinnings or drilling, so environmental damage should be minimal, officials said.

Simply setting a turbine down gives the PUD some flexibility to move it around later, said Craig Collar, a senior manager of energy resource development with the PUD.

If the trial is successful, a much larger turbine farm in Admiralty Inlet could be used to generate a lot renewable energy for customers, officials said.

Chris Fyall: 425-339-3447, cfyall@heraldnet.com.

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