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San Francisco Weighs Harnessing Tides for Electricity by Reuters Environmental News Network - May 7, 2003

SAN FRANCISCO -- The powerful ocean tides that surge daily beneath San Francisco's Golden Gate Bridge may be tapped to generate electricity.

San Francisco's Board of Supervisors voted unanimously on Tuesday to launch a $2 million pilot project to study harnessing wave energy to generate enough electricity to light more than 750 homes in this city of 790,000 residents.

The project, which also needs environmental and other government approvals, is believed to be one of the first efforts in the United States to generate commercial tidal power, said Mark Westlund, a spokesman for the city's Department of the Environment. The tides that ebb and flow through the narrow Golden Gate would be channeled through an underwater concrete passageway with no moving parts, building up pressure and creating a suction effect to spin on-shore generators, Westlund said, adding that it would not interfere with busy shipping lanes.

Each tidal cycle pushes 400 billion gallons of water through the Golden Gate, enough to generate an estimated 2,000 megawatts, or more than twice the city's peak power demand. California was hard hit by blackouts in 2000-01, prompting the state and its cities to double their efforts to find new, environmentally friendly energy resources.

San Francisco has not nailed down project funds or formally selected a developer but has been looking at technology developed by HydroVenturi Inc., based in London and Los Gatos, Calif., Westlund said. "Tidal power is a clean energy resource we definitely want to consider for adding to our electricity system," said Westlund. The city is also weighing solar power.

New developments in tidal power technology are being studied for possible projects in Canada, Norway, and Britain.