DECEPTION PASS – Any sailor worth his or her salt knows not to run against the tidal currents that rush through this narrow canyon.
At 8 knots, or nearly 10 mph, the water is moving fast.
Snohomish County PUD officials want to find out if they can use that tidal energy to generate electricity. To do that, they need to know exactly how fast the water is moving.
So in 10 days they will begin taking current speed measurements, first at nearby Admiralty Inlet and then at Deception Pass.
“Velocities (here) are higher than anywhere else in Puget Sound,” said Craig Collar, senior manager of energy resources development at the PUD.
The current in Deception Pass is notorious for creating whirlpools. If they are too strong, turbines have no future there, he said.
The utility plans to use acoustic Doppler current profiling, a type of sonar, to measure current speeds through the narrowest part of Deception Pass. That’s where the water appears to move quickest.
The PUD thinks the area where turbines may fit best is about a half-mile long stretch that is underneath the Highway 20 bridge.
The water measurements will be fed into a modeling program that the University of Washington is developing for the utility.
“We’re already moving on the model,” said Brian Polagye, a research associate with the university’s Department of Mechanical Engineering.
He said the field measurements would be used to improve the model, which then could be used to pinpoint where to place fields of underwater turbines.
One measuring technique, called over-the-side testing, involves hanging a device over the side of a boat and then dragging it through the water.
“It will measure the velocity all the way to the sea bottom,” Collar said.
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.
To measure how speeds change with the tide, a stationary probe will be left in the water for 28 days, or two complete tidal cycles.
The PUD earlier this year received federal permits to explore planting fields of tidal turbines in Deception Pass, Admiralty Inlet, Guemes Channel, San Juan Channel, Spieden Channel, Agate Passage and Rich Passage.
The utility sees as many as 1,662 turbines on the bottom of Puget Sound, according to permits approved by the Federal Energy Regulatory Commission.
The turbines would be staggered in rows aligned to capture the strongest, most consistent currents. Sizes would vary. Many could be 100 feet tall with their slow-turning blades as big as 66 feet in diameter.
Together the turbines would generate about 100 megawatts of electricity on average, enough for 60,000 homes – about every house and apartment in Mukilteo, Everett and Marysville.
Area tribes and environmental groups have been watching closely. They worry about the impact to endangered chinook salmon, orcas and other marine wildlife.
“We’re still concerned over what the impacts will be on our fishermen,” said Daryl Williams, environmental liaison for the Tulalip Tribes.
He said fishing opportunities for the tribes have dwindled and they don’t want to lose any more fishing grounds.
“We can’t fish were there are turbines,” he said. “You can’t have your gear around a turbine.”
Some worry that federal and state legislators are moving too fast to grant tax breaks for the development of tidal energy and other forms of water-based electricity generation.
The environmental impacts of the emerging technology need to be studied first, said Bruce Wishart, policy director for People for Puget Sound.
“We think there’s probably a way to do this correctly,” he said.
U.S. Rep. Jay Inslee, D-Wash., introduced a bill earlier this year to promote the development of tidal and wave energy. His bill would make low-interest loans available for developing ocean-based renewable energy technology and would give tax credits to utilities that buy or develop the electricity. He also proposes to spend $50 million per year on ocean-energy research for 10 years.
State Sen. Steve Hobbs, D-Lake Stevens, has proposed legislation that would give tidal energy the same tax exemptions that wind and solar energy currently enjoy.
Reporter Lukas Velush: 425-339-3449 or email@example.com.