Tidal power: another blessing from Puget Sound?

The big Snohomish Public Utility District will seek federal permission to install tidal power turbines in Admiralty Inlet. Not everyone is sure tidal power would work out well.

Crosscut archive image.

UW researchers deploy the Sea Spider in Admiralty Inlet.

The big Snohomish Public Utility District will seek federal permission to install tidal power turbines in Admiralty Inlet. Not everyone is sure tidal power would work out well.

Its 6 a.m. at Point Hudson, a sandy spit that stretches from Port Townsend into Admiralty Inlet. Brian Polagye, a University of Washington researcher from the Applied Physics Laboratory, stands on the back deck of the 50-foot aluminum research boat, the M/V Jack Robertson. He has been up for most of the night prepping instrumentation for a research deployment.

Since 2005, Polagye has been studying the Puget Sound as a potential site for tidal power, energy garnered from turbines placed on the seabed. The Jack Robertson rumbles to a start and we leave the dock headed for the middle of the channel.

Admiralty Inlet is situated between Port Townsend and Whidbey Island. It is the geographic bottleneck that water flows through between the Salish Sea and the Puget Sound, from the San Juan Islands to Olympia. If the Puget Sound were a human heart, Admiralty Inlet would be one of the pumps, constantly pulling water in and flushing it back out in never-ending 12-hour cycles.

This morning, Polagye is prepping what looks like a giant orange camera tripod called the Sea Spider. On this piece of equipment is a collection of PVC tubes and boxes containing instruments that will collect data about ambient noise, current velocity, water quality, and the presence of tagged fish and harbor porpoise. This data is used to understand the Admiralty Inlet seabed and predict what impacts tidal turbines might have there.

This spring, the Snohomish Public Utility District, who Polagye is contracted through, will submit its final license application to the Federal Energy Regulatory Commission (FERC) to install two test turbines on the bottom of Admiralty Inlet. The turbines would look like large “donut-shaped” rings, spanning 33 feet across, positioned several feet above the sea floor. As tides rise and fall, each turbine would generate an average 100 kilowatts of power, enough power for 50-100 homes.

Polagye describes tidal energy as “a blank canvas.” When I ask him what he thinks is exciting about it, and why it’s so new, he answers: “Tidal energy is difficult to do. It’s a really tough operating environment. It’s been called more difficult than going to the moon.” Turbines at Admiralty Inlet would sit 180 feet below the water surface and have to withstand the power of Puget Sound's currents.

For utilities like the PUD, the promise of tidal energy lies in its predictability. The PUD is working with a number of partners on technical aspects of its effort, including Pacific Northwest National Laboratory's Marine Sciences Laboratory.

“Supposing you have a wind turbine spinning, and the wind drops, you have to instantly bring something up online. What if the only thing you have is a coal fired power plant? That’s not very helpful,” says Andrea Copping. Copping is a biological oceanographer at Pacific Northwest National Labs and studies the potential risks and benefits of this emerging technology.

Puget Sound contains a number of sites with strong tidal currents and strong potential for energy generation, the main two being Admiralty Inlet and the Tacoma Narrows. Deception Pass, the Puget Sound’s closest thing to a whitewater river, has been largely abandoned as a site due to its washing machine-like turbulence, a characteristic too unpredictable for turbines to function well in.

Aboard the deck of the Jack Robertson, the Sea Spider has been lifted 10 feet in the air, where it hangs off the ship’s stern. It sways for a moment in mid air and then disappears in the darkness below, where it will sit gathering numbers and sounds and video until it is fished out next May with its cache of new data.

Public reaction to tidal energy development has varied. At community meetings, Polagye recalls sentiments ranging from “Why do you hate the environment?” to “Are you going to study this thing to death, or are you actually going to generate some power?” Local environmental groups, too, have shown hesitation.

Paul Dye is the director of Marine Conservation at Washington’s chapter of The Nature Conservancy (TNC). According to Dye, TNC’s main concern is that tidal energy installations will occupy an already-busy environment, which includes critical marine habitats, animal migratory passageways, and commercial uses like ferry boats and shipping lanes. “There’s a lot about the field that’s attractive," he says, "but the problem with it is we don’t have any experience with it.” For Dye, tidal power needs to be developed in concert with the environment and other users.

To Polagye, Admiralty Inlet is an ideal site for tidal turbines. It’s an area with a rocky, hard bottom, without much resident sea life.

Dye, however points out that these chokepoints through which large amounts of water flow serve as the migratory passageways for any sea life going in and out of the Puget Sound, be it salmon, stellar sea lions, or orcas. He says installing tidal infrastructure in all of them would be like “building a campground in every piece of old growth forest you have in the park."

“The bottom line,” Dye explains, “is that we don’t have enough research.”

Herein lies the subtle rift between environmental groups like TNC and researchers like Polagye: One side wants to know the environmental effects of tidal turbines, while the other says a definitive impact cannot be known until the equipment is installed.

Both sides agree on the goal: cleaner, sustainable energy, but the means of getting there is less clear.

Turbine installation is, however, a gradual process. If FERC approves the pilot project in the coming months, the first turbines will be installed on the sea floor and studied for three to five years in order to thoroughly understand their site impacts. Only then would a larger array be installed.

To date, FERC has issued permits for tidal projects in sites including Maine’s Bay of Fundy, the East River in New York, and Cook Inlet in Alaska. This would be the first project licensed in Washington state.

“Once these turbines are out there, we can actually begin to test our hypotheses about what may happen, and gather real information,” explains Copping. “And again, unlike a hydro dam, you put these things in and if something terrible happens, you pull them out.

"As we recognize the need to get off our carbon-based economy or at least cut back on our carbon based economy, there is real promise from this truly renewable source."


Please support independent local news for all.

We rely on donations from readers like you to sustain Crosscut's in-depth reporting on issues critical to the PNW.


About the Authors & Contributors