PUD moves ahead on tidal project

Tidal-power devices being studied and tested for world marketing are in line with the Snohomish County PUD's schedule for constructing a tidal-power project somewhere in Puget Sound, officials say.

PUD officials toured manufacturing facilities and testing sites of front-running tidal-power-device companies while on a European tour the past two weeks. Such companies as Open Hydro and Marine Current Turbines (MCT), both United Kingdom-based and considered tidal-market leaders, likely could meet the PUD's requirements for tidal devices, said Craig Collar, the PUD's senior manager of energy-resource development.

Open Hydro is testing a device that looks similar to a doughnut, with a turning wheel inside that funnels water to generators for electricity production. MCT's devices look like underwater versions of propellers used on wind farms.

The PUD is moving forward with initial studies of seven sites throughout Puget Sound. Last week, it removed testing equipment from the bottom of Admiralty Inlet and Deception Pass, the first of the sites where tidal-current measurements are being made to see if either are conducive to a future tidal-power project.

The PUD will look at five other sites — Speiden Channel and San Juan Channel off San Juan Island, Guemes Channel near Anacortes, and Agate Passage and Rich Passage along Bainbridge Island — beginning in the spring. It will take about three years, officials have said, before they will know which sites work best. At that point, the PUD will begin to decide which equipment is best for a location.

"It's pretty unlikely the same devices will be appropriate for all seven sites," Collar said. "But after visiting with some of the manufacturers, we're confident our overall study plan won't change."

Different devices might be necessary because of the different currents being measured by the PUD with help from the University of Washington. At Admiralty Inlet, where waters are about 250 feet deep, currents are moving faster than initially expected, said Brian Polagye of the UW's mechanical-engineering school. The PUD is studying an area a little more than 1.5 miles wide between Admiralty Head and Point Wilson, and about 2.5 miles in length.

"Overall power capacity is based on how strong the currents are," Polagye said. "And based on what we're initially seeing, that could be two or three times what we initially suspected."

While Deception Pass shows the fastest currents, it could be difficult to build a tidal-power project there, officials have said. Mainly, a tidal-power turbine would need to be able to withstand the strong currents and there are issues related to the water being sandwiched between land owned by the state.

The UW hopes to have preliminary data available in a report to the Bonneville Power Administration, which is funding part of the initial studies, by the end of the month. Meeting that deadline is important to show Bonneville and other potential funders that the PUD is on schedule.

Total costs for preliminary studies of the current this year are expected to be near $285,000. Bonneville, which supplies more than 80 percent of the PUD's energy now, is paying about $185,000 of that.

"Where outside funding is going to be so necessary is when we're ready to put a device in the water for a pilot project," Collar said. "That's when the costs for installation and monitoring are going to go up quickly."

Collar said the PUD shouldn't have to ask its customers to bear all of those costs, especially since other utilities and institutions will gain from the Puget Sound studies under way.

"We're so appreciative of the work that the UW and others are doing, but that work is not just a benefit to us," he said. "It also will help many others understand better Puget Sound."

Christopher Schwarzen: 425-745-7813 or cschwarzen@seattletimes.com