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Power Plant Could Harness
Tidal Energy of Narrows

by Les Blumenthal
The News Tribune, July 18, 2006

WASHINGTON - The Tacoma Narrows holds "significant promise" as a site for one of the nations first projects to generate electricity by tapping the tides, according to a new report.

But the cost of the power it would produce could be pricey. And even though they already have a preliminary permit from federal regulators, Tacoma Power officials remain cautious about committing $4.2 million for a pilot plant.

If a full-scale project was developed, it could involve 64 underwater turbines near the north end of the Narrows, according to the study from the California-based Electric Power Research Institute.

Each turbine would be equipped with two blades, each almost 60 feet long. The blades would rotate at about 10 revolutions per minute and generate enough electricity to power nearly 11,000 homes. The project would cost an estimated $103 million.

Tacoma Power officials have met with representatives of two companies that manufacture tidal generators, including one installing a test turbine in New York's East River.

"If this pencils out, it is a good option for green power," said Debbie Young, natural resources manager for Tacoma Power.

But the utility wants to conduct more studies of the tidal flow through the Narrows, including one using acoustic Doppler radar, before deciding whether to proceed with a pilot project, Young said.

"There are a lot of questions that need to be answered, but it is an exciting opportunity," she said.

The Tacoma Narrows is one of a handful of sites in Puget Sound where tidal generators could be installed.

The Snohomish County Public Utility District seeks preliminary federal permits for five sites, including Admiralty Inlet, Deception Pass and Agate Passage.

A possible project near Point Wilson could involve 450 turbines and generate enough electricity to power 50,000 to 60,000 homes.

The new manager of Snohomish PUD's, Steve Klein, championed the Tacoma Narrows site while serving as superintendent of Tacoma Power.

The Tacoma Narrows site has been more extensively studied and is further along the road to possible development than others in Puget Sound.

If Tacoma decides to proceed, it likely would seek partners or turn to the federal Department of Energy or the Bonneville Power Administration for financial backing.

Far and away the best site for tidal electricity generation in North America is the Bay of Fundy in Nova Scotia, where the tidal flows are "so large you can hear them," said Roger Bedard, who overseas tidal and ocean programs for the Electric Power Research Institute.

Yet when it comes to sites in the United States, Bedard said, the Tacoma Narrows stacks up favorably to other areas institute has studied, including the Knik Arm in Alaska and the Golden Gate in California.

"It's a good tidal site, not the best, but a good tidal site," Bedard said of the Narrows. "Absolutely, Tacoma (Power) should pursue this."


In addition to having strong tidal flows, there are ample transmission lines adjacent to the Narrows to carry the electricity the underwater turbines would produce. The nearby Port of Tacoma could be used to provide logistical support.

Development plans center on Point Evans near the north end of the Narrows where tidal flows are strongest. The seabed at Point Evans is deep enough so the underwater turbines would not interfere with shipping traffic through the Narrows, including deep-draft container ships headed for the Port of Olympia.

While the Electric Power Research Institute study said floating kelp could tangle turbine rotors, it did not address other potential environmental impacts of the turbines, such as the effects on migrating salmon, whales and other fish and marine mammals.

The National Oceanic and Atmospheric Administration, along with the Washington state departments of Fish and Wildlife and Natural Resources, were granted "intervenor" status when the Federal Energy Regulatory Commission approved the three-year, preliminary permit in February.

Young said building the demonstration plant might be the only way to assess the effects on the environment. "If it makes economic sense, we will investigate the environmental impacts," she said.


Electricity produced at a Tacoma Narrows tidal generating project would cost nearly the same as wind power and solar power, the Electric Power Research Institute study said. The cost would be between 6 and 9 cents per kilowatt-hour, but that does not include the cost of designing, permitting and constructing the plant and the transmission lines to carry the electricity it produces.

When those costs are included, the tidal-generated power would be about one-third more expensive than Tacoma Power charges its residential customers.

Young said the study's cost estimates has not dampened Tacoma Power's interest in a tidal generating plant. "We need to take a close look," she said.

Congress has granted tax incentives to lower the cost of producing solar and wind power. But it has not provided such incentives to developers of tidal or ocean wave generation projects. If such tax incentives were offered, Bedard said, the power produced at the Tacoma Narrows would be competitive with other green power sources.

Bedard also said Tacoma Power and other public utilities would be able to borrow money for a full-scale project at lower interest rates than private utilities.

"We need to use indigenous resources that Mother Nature gave us," Bedard said. "I don't like sending money to Saudi Arabia."

Four answers about tidal power

How does it work? The flow of the tides rotates large blades attached to a turbine that turns a generator, producing electricity.

How much power? Tidal flows in the Tacoma Narrows optimally could produce 106 megawatts of electricity, about a 10th of the power produced at a nuclear power plant or a fifth of the power produced at a medium-sized gas- or coal-fired plant. But because of engineering and environmental limitations and other concerns, only about 15 percent of the available power might be harnessed. Nevertheless, that would be enough to serve nearly 11,000 homes.

Where are some tidal power plants? There is a large plant in France and a smaller one in Nova Scotia, but they use a system of dams to impound tidal waters before releasing it through generators. In the United States, a demonstration plant is being installed in New York's East River.

How much would it cost? A demonstration project in the Narrows would cost about $4.2 million and a full-scale project would cost about $103 million.

Les Blumenthal
Power Plant Could Harness Tidal Energy of Narrows
The News Tribune, July 18, 2006

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