Agencies looking to develop power from within the Earth

Heat that’s been trapped for eons beneath the Earth’s surface could be used to power a growing amount of city work if state energy regulators approve a San Francisco grant application.

A seven-person California Energy Commission panel is scheduled this week to assess applications from groups seeking a share of $5.7 million in grants earmarked to develop geothermal energy sources, commission spokesman Adam Gottlieb said.

The San Francisco Public Utilities Commission, Sacramento Utilities District and Richmond-based GeothermEx Inc. filed a joint grant application seeking roughly $500,000 to fund geothermal energy mines. Each partner would also contribute funds, including $80,000 from the SFPUC.

The nonrenewable energy would be mined from SFPUC-owned land west of the Sierra foothills and from Sacramento Utilities District-owned land, SFPUC spokesman Tony Winnicker said.

The electricity would be produced from steam and naturally occurring hot water in wells up to 12 inches wide, said GeothermEx Vice President Ann Robertson-Tait said. The SFPUC powers city government buildings and sells power to other municipalities using hydropower created at its Hetch Hetchy dam in Yosemite, said Barbara Hale, SFPUC general manager of power.

The SFPUC is forced to buy electricity when the water flow slows, including some geothermal energy, but Hale said the agency hopes to plug that gap by creating new energy sources.

It’s not known how much geothermal energy could be produced by the SFPUC, Hale said, and she added there’s nothing special about the land proposed to be mined.

“There is geothermal potential everywhere,” Hale said. “The issue is, how deep do you have to dig before you tap into a hot source?”

The underground heat has existed since the planet was formed, Robertson-Tait said.

City Environment Director Jared Blumenfeld said one geothermal technique that drills two- to three-miles deep to reach a “huge amount of energy” would not be tested because it can create “mini-earthquakes.”

Pacific Gas & Electric Co., which powers most of The City’s homes and businesses, uses geothermal energy for 3 percent of its electricity, according to spokesman Joseph Molica.

Nearly 5 percent of California’s electricity comes from geothermal sources, according to California Energy Commission figures. The state produces about two-fifths of the world’s geothermal power, commission figures show.

Commission spokesman Gottlieb said grant winners will be announced in April. He said the grants are funded by federal royalties levied on geothermal energy producers.

jupton@examiner.com

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