Tidal-energy project stays on course after UW's tests on Puget Sound

A tidal-energy pilot project is one step closer to launching in Puget Sound.

Researchers from the University of Washington spent four days last week on board a vessel collecting data, capturing underwater video and measuring velocity in Admiralty Inlet between Port Townsend and Whidbey Island. The channel likely will host one of the nation's largest tidal-energy projects.

UW researchers said last week's tests confirmed the location is ideal for capturing tidal energy. The team gathered some initial data and will return two more times this year to monitor the site.

"The emphasis here is on learning," said Jim Thomson, an oceanographer at the UW's Applied Physics Lab.

Strong currents in Puget Sound are considered among the best in the country for harnessing tidal energy. But the industry is young, and experts acknowledge the technology and its possible impacts on the environment must withstand further testing.

That's why the Snohomish County Public Utility District (PUD) is pursuing a pilot project in Admiralty Inlet. In two years, officials expect up to three turbines will be placed on the seafloor to produce 1 megawatt of energy, or enough to serve about 700 homes.

The PUD has chosen a turbine design that spins either way depending on the tide's direction. An underwater cable would feed energy to transmission lines on Whidbey Island. The blade tips are enclosed, and the turbine can be placed on the seafloor with no drilling or pilings, said Craig Collar, the PUD's senior manager of energy-resource development.

"This is a very straightforward device, very robust," he said.

The pilot project is awaiting federal, state and local permits and an operating license. Once the project is in, the PUD will use it mainly for research, monitoring performance, costs and environmental effects. A large-scale tidal farm could be established in the future, he said.

But for now, UW researchers will continue gathering data in Admiralty Inlet to find the best place for the pilot project.

Last week, they spent 12 hours each day aboard the R/V Jack Robertson, recording video footage of the sparse, rocky seafloor and collecting data. Researchers sent down a tripod-shaped device that measures background noise, velocity and temperature, among other things. In August they will retrieve the data, then deploy the device once more.

Researchers were surprised at the current's strength in the inlet. Slack water between tidal cycles lasted only about five minutes, said Brian Polagye, a UW research assistant professor in mechanical engineering.

"It's hard for surveying, good for energy," he said.

Michelle Ma: 206-464-2303 or mma@seattletimes.com