Nov 20 - The Sacramento Bee

If anyone needs another means to experience the energy of the Golden Gate, the narrow channel flowing between the Pacific Ocean and San Francisco Bay, they someday may find it from their nearest electrical outlet.

That is the hope of San Francisco officials, who are now studying ways to harness the tremendous power of daily tidal shifts deep in the Golden Gate's waters.

In September, San Francisco Mayor Gavin Newsom announced the city would commit $145,000 to a feasibility study on generating electricity from the channel's tidal and wave energy.

If all goes as planned, the first test of such a system could take place in 2009. That may seem ambitious, given that capturing the power of tides has yet to be attempted in similar waters.

But there is increasing interest in developing cost-effective technology to do just that as oil prices move higher and the dangers of global warming become more widely known.

Scientist and engineers in San Francisco and elsewhere are pondering innovations that could provide electricity from underwater turbines akin to the windmills of Altamont Pass.

"We want to do everything, no pun intended, in our power to make sure that the city is using as much renewable power as possible," said Susan Leal, general manager of San Francisco's Public Utility Commission.

"For tidal (power), even though it looks further out into the future, it still warrants investigation."

A consortium of European governments -- including Britain, Portugal, Denmark and Norway -- have set up a lab at the Orkney Islands, north of Scotland, where wave devices to generate power are being tested.

Meanwhile, a number of companies have obtained temporary federal permits over the past two years for several locations around the United States where tidal or wave energy may be developed.

Eleven three-year permits already have been issued by the Federal Energy Regulatory Commission, including one for San Francisco Bay, and another three dozen are pending. But no one has applied for development licenses, which would authorize construction.

The Electric Power Research Institute, an industry-sponsored group, jumped into the debate last June with a report concluding that wave and tidal energy is feasible in several U.S. locations, including the Golden Gate.

In New York City, a private firm will soon be installing the first of what could be scores of underwater turbines in the East River channel between Roosevelt Island and Brooklyn.

The devices will provide relatively small amounts of electricity. But testing over the next 18 months will help resolve questions that include environmental impacts and commercial viability, said Trey Taylor, president of New York-based Verdant Power, which is building the East River turbines.

"We're 'damless' hydropower," said Taylor. "The information that we gather ... can be very applicable to some extent to the Golden Gate."

Exploiting the power of four-times-a-day tidal surges at the Golden Gate, involving hundreds of billions of gallons of water, will not be easy.

The channel is a bit more than a half-mile wide and as much as 311 feet deep. Vessels of all sizes traverse it daily. Its beauty and environmental importance are key elements in the discussion, as are the myriad governmental agencies that a tidal power proposal would have to navigate.

Still, experts appear convinced of the potential. The Electric Power Research Institute study, for example, estimated that an average of 35 megawatts could be produced there, enough to supply 27,000 homes.

"The technology is relatively proven and feasible," said Jared Blumenfeld, director of the San Francisco Department of the Environment.

"There needs to be more work done," he added. "But it's definitely at a stage where it works, where cost effectiveness of the power produced is low enough to be significantly more competitive than solar and even more competitive at the moment than wind."

The underwater turbines could include propellers connected to a generator and cables to send electrical current onshore.

But no one design has become universally accepted, said Robert Thresher, the federal government's lead wave and tidal energy expert, even though he directs the U.S. National Wind Technology Center in Golden, Colo.

"It's a very creative period," he said. "There's no right way to do it. There's not a lot of experimental data on how these perform in the real world."

But, Thresher added, wind turbine technology stood at the same point a generation ago until testing and experience brought researchers to a consensus on how they should be designed. The same will occur with tidal generators, he said.

The city study is due next summer. If it shows promise, officials hope to get a demonstration project up and running in three years. The city also is interested in producing power from waves that strike Ocean Beach, but that notion is not being explored for now.

If the tidal and wave technology ultimately works, economically and environmentally, it could become a source of renewable electricity for many of the world's inhabitants, a large percentage of whom live in coastal cities near rivers.

"As the tide comes in and out through a harbor, you can tap that and get electricity from it," said Thresher, "which is exactly what San Francisco is talking about."

About the writer:

* The Bee's Herbert A. Sample can be reached at (510) 382-1978 or hsample@sacbee.com.

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