Tidal power studied as power source

SAN FRANCISCO, Calif.—The San Francisco Public Utilities Commission selected URS Corporation to conduct a feasibility study of harnessing tidal flows in San Francisco Bay through the Golden Gate as a source of clean, sustainable energy. Tidal flows in and out of San Francisco Bay consistently generate high-velocity currents in the Golden Gate narrows. High velocity produces a concentration of tidal energy, some of which can theoretically be captured by submerged, in-stream tidal energy devices. These devices would be submerged at depth in the 300-foot-deep passage to avoid visual impacts near the Golden Gate Bridge. Most in-stream devices look like the underwater equivalent of wind farm turbines.

Key issues to be addressed in the study are how much energy is available, how much can be extracted without adversely affecting the tidal exchange, what the impact might be on protected fish and mammal species, and whether the concept is economically viable.

The scope of work of the feasibility study is divided into the following three tasks:

• perform a technology screening assessment by development of a feasibility ranking matrix for existing and promising technologies;
• conduct computer modeling of the Bay/Golden Gate system to assess total extractable energy and the percent of energy that can be extracted without adverse impacts on the Bay’s tidal prism and ecosystem; and
• identify and hold meetings with stakeholders.

The study will produce recommendations on which technology should be carried forward in a pilot study near the Golden Gate. The feasibility project is part of an overall plan by Mayor Gavin Newsom to position San Francisco as a global hub for creation and use of clean energy.