Tides around Golden Gate could become energy source

San Francisco mayor Gavin Newsom is calling for a study on the feasibility of putting an energy harvesting system in the city's famed Golden Gate.

In general, wave power is considered one of the least promising alternative energy ideas. It's expensive, and keeping the system working isn't easy.

Still, it's being tried in some areas where tides are strong. Ocean Power Delivery, based in Edinburgh, Scotland, says its Pelamis system can harvest electricity from waves safely and efficiently. It's in the midst of installing a system off the coast of Portugal.

Despite having a small tidal range, relative to other regions, the force of water flowing through the Golden Gate is extreme. San Francisco Bay sees a massive amount of water get pushed through a very narrow strait. Approximately 528 billion gallons of water rushes through the strait every six hours.