Feds look to the ocean for clean energy as scientists debate wave power potential.
Thursday, February 9, 2012
Offshore oil drilling doesn’t stand much of a chance in the protected waters of Monterey Bay. But as the U.S. Department of Energy eyes the sea for renewable energy, local shores are strong contenders.
Apart from Alaska, California’s Central Coast has the nation’s highest potential for wave power, according to a report by Palo Alto-based Electric Power Research Institute. EPRI project manager Paul Jacobson estimates the Central Coast’s outer continental shelf packs about 21 gigawatts per year in available wave energy, the rough equivalent of 21 nuclear power plants.
A four-month trial on the San Luis Obispo coast last summer yielded encouraging results for what’s called wave energy sequestration technology. Bobbing buoys send hydraulic pressure through a hose to a high-tech water wheel, which drives a generator.
“We got quite a bit more output than we expected,” says Phil Kithil, founder of Santa Fe-based Atmocean Inc.
The DOE also commissioned a study on tidal energy, which harvests power from ocean currents using devices similar to underwater windmills. Georgia Tech engineering professor Kevin Haas, who led the study, says tidal power could theoretically produce more than 50 gigawatts a year. The tech is at its best when a large volume of water rushes through a narrow point, like under the Golden Gate Bridge, he says. Since Monterey Bay doesn’t have that bottleneck, it wouldn’t be a strong candidate for tidal power.
A third source on DOE’s radar: ocean thermal energy conversion, which generates electricity through use of ammonia steam. The concept is even more far-out than wave or tidal energy, according to Howard Hanson, scientific director for the Southwest National Marine Renewable Energy Center; no one has even designed a prototype. Ocean thermal works best when the surface water is much warmer than deep water, Hanson says, so California stacks up poorly compared to places like Florida and Hawaii.
Andrew Hamilton, mechanical engineer at the Monterey Bay Aquarium Research Institute, sits on the National Research Council committee that’s assessing the reports. He won’t comment on the committee’s deliberations, but a letter sent to the DOE in July suggests members are skeptical. The estimates of total power potential should be much lower, it warns. It’s not realistic to assume, for example, that energy-collecting buoys would span the West Coast.
The studies’ authors agree their figures are only theoretical maximums, useful mainly for identifying the best ocean energy sites. “The potential is vast and enormous,” EPRI spokesman Chris Mahoney says, “but no one’s going to suggest you could power the entire state of California with wave power.”