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Published: Thursday, September 20, 2007, 5:33 p.m.

PUD tidal power passes first test

Currents in Sound are strong enough to make electricity

  • Kevin Nortz / The Herald
A team of oceanographers hired by Snohomish County PUD retrieves a device that measured water current velocity in Admiralty ...

    Kevin Nortz / The Herald A team of oceanographers hired by Snohomish County PUD retrieves a device that measured water current velocity in Admiralty Inlet for one month. The data collected will be used to determine whether tidal turbines would be effective at several locations in Puget Sound.

ADMIRALTY INLET — Tidal currents that could generate electricity for thousands of homes and businesses run stronger than expected here, pumping life into Snohomish County PUD's bid to embed thousands of tidal turbines in the bottom of Puget Sound.
PUD officials on Wednesday were on a chartered boat, touting the potential of tidal energy, while nearby oceanographers fished current-measuring devices from the bottom of Puget Sound.
The devices measured tidal currents for 28 days, or two tidal cycles, in Admiralty Inlet and Deception Pass.
Those data will be fed into models intended to show the utility where it could place turbines, how many and how big, deep below the sea.
Preliminary data collected in July and Aug≠ust gathered by a different device that also measures tidal currents suggest Admiralty Inlet could produce more electricity than initially estimated, said Brian Polagye, a research associate with the University of Washington's Department of Mechanical Engineering.
The turbines the PUD wants to use are like underwater windmills fixed to the seabed. Tidal currents turn the turbines, and the natural energy would be converted into electricity. Turbine sizes would vary. Many could be 100 feet tall with their slow-turning blades as big as 66 feet in diameter.
They would be staggered in rows aligned to capture the strongest, most consistent currents.
"Hot spots" where tidal currents run strong are widespread in Admiralty Inlet, something that the PUD did not know when it proposed making the busy waterway the focal point of its foray into tidal power, Polagye said.
"I'd say that the numbers we have been getting are pretty considerable," he said. "It's looking good."
In filings with federal regulators, the PUD estimated it could generate 100 megawatts of electricity at seven locations in Puget Sound, enough for 60,000 homes, or about every house and apartment in Mukilteo, Everett and Marysville. That initial assessment suggested Admiralty Inlet could produce 75 megawatts of electricity, more than the potential identified at the other six sites together.
"We're very encouraged by the results we're seeing, in that there could be more potential in Admiralty Inlet than we anticipated," said Neil Neroutsos, a utility spokesman.
Tidal current speeds are measured using an acoustic Doppler current profiling device, a type of sonar, to measure current speeds, said Jeff Cox, president and senior oceanographer at Evans-Hamilton Inc., a consultant hired by the PUD to measure tidal currents.
The speed of the water is obtained by measuring how noise bounces off bits of plankton and other microscopic material suspended in the water column, he said.
Getting the device to surface on Wednesday turned out to be a tricky operation. Several times Cox's crew failed to get it released from the bottom of Puget Sound, about 250 feet below where ocean-going cargo ships were cruising past.
"There it is, right there," Cox said. "The orange ball."
The PUD is in the beginning stages of a three-year study into whether tidal power is feasible in Puget Sound.
The utility is launching studies on the environmental impacts of tidal power and which kind of tidal turbines would be best for Puget Sound. It's the biggest proposal of its kind in the U.S.
Area tribes and environmental groups have been watching closely. They worry about the effect on endangered chinook, orcas and other marine wildlife.
In addition to Admiralty Inlet and Deception Pass, the PUD's study sites are Spieden and San Juan channels in the San Juan Islands, Guemes Channel near Anacortes, Agate Passage near Bainbridge Island and Rich Passage near Bremerton.
Reporter Lukas Velush: 425-339-3449 or lvelush@heraldnet.com.
Story tags » PUDPuget Sound

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