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Sonoma Clean Power eyes North Bay geothermal

SANTA ROSA -- Sonoma County's startup public power agency is set to consider the purchase of a portion of its electricity supply locally from the Geysers, the world's largest complex of geothermal power plants located along the Sonoma and Lake County border, according to material presented to the agency's governing board.

The contract with Calpine Energy Service would constitute approximately 10 percent of Sonoma Clean Power's electricity through 2023, ramping up to 18 megawatts -- 158,000 megawatt-hours annually -- as the renewable energy-focused power provider increases its customer volume in the coming years. Houston-based Calpine operates 15 geothermal power plants at the Geysers, with a combined capacity of 725 megawatts.

The item does not disclose the wholesale pricing per megawatt-hour currently under discussion, but notes that agency staff are currently acting within an approved framework for negotiations that would set a ceiling for average retail rates that are equal to or below the anticipated 2014 average rate from Pacific Gas & Electric Co. -- 9.72 cents per kilowatt-hour, or $972 per megawatt-hour.

The proposed agreement with Calpine is separate from the agency's current negotiations for a primary power supply contract, and would contribute significantly to its goal of launching with a baseline electricity mix of at least 33 percent renewable energy on May 1. Sonoma Clean Power will be the second "community choice aggregation" agency after Marin County-based MCE Clean Energy and, like MCE, will deliver electricity to its customers over the grid largely maintained by PG&E.

Three wholesale power providers are considered finalists for Sonoma Clean Power's primary contract, which will exist for a three-year term: Constellation Energy, NRG Energy and Direct Energy. Calpine was also among an initial group of wholesale power providers vying to supply the brunt of the agency's electricity needs at launch.

The agency will begin serving an estimated 20,000 customers in 2014 -- largely commercial ratepayers. Service will gradually roll out throughout the county, though Rohnert Park, Petaluma, Cloverdale and Healdsburg have not approved rollout to their residents and businesses. Healdsburg currently operates its own utility, and has done so for around 50 years.

Sonoma Clean Power is expecting to purchase 20,599 megawatt-hours of electricity in its first month of operation, and nearly 400,000 in its first year. The value represents electricity usage over time, and will constitute around 567,750 megawatt-hours in 2015 and 496,900 in 2016.

On megawatt of standing production capacity is roughly adequate to power 1,000 homes, and one megawatt is equivalent to 1,000 kilowatts. Calpine currently has pre-approval to construct two new 49 megawatt plants at the Geysers, though the company has said construction will proceed amid heightened demand.

MCE, with service available in all Marin County municipalities and the city of Richmond in Contra Costa County, entered into a power service agreement with Calpine this year. The contract includes a short-term, three-megawatt deal through 2017, and an annual 10 megawatt deal for ten years after that.

Calpine employs around 300 people at the Geysers, an area encompassing around 45 square miles. Harder rock near the surface of the ground contains pressure generated by a natural underground heat source, allowing the construction of power plants that harness that pressure for electricity generation.

Recycled water from Santa Rosa is injected underground at the site to "recharge" its underground aquifer. Calpine's Geysers plants are attributable for around 20 percent of renewable energy production in California, and are considered a standout renewable source due to the round-the-clock production of energy.

The Sonoma Clean Power Authority is scheduled to consider the agreement on Nov. 21. Staff have been pre-authorized to go forward with the separate primary contract without full board approval, with a decision expected in the coming weeks.

Costs for residential and commercial ratepayers are expected in January. Those eligible customers will be able to "opt-out" and remain with PG&E, but will otherwise be enrolled automatically.

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