Calpine plans $700 million Geysers geothermal power expansion  

The North Bay Business Journal reports that the world's largest geothermal power plant will expanded by 98 MW - Calpine plans $700 million Geysers expansion.

Calpine Corporation, the nation’s largest renewable geothermal power producer, plans to build two new power plants adjacent to its existing Geysers steam field in Sonoma and Lake Counties designed to generate a total of 98 megawatts of additional clean energy, pending regulatory approvals. ...

The Geothermal Operator Corporation (GOC) and the Central California Power Association (CCPA) previously developed this site. These firms built their first plant in 1989 with a capacity of 135 megawatts. Due to a sharp decline in natural steam conditions, the plant was decommissioned and steam wells were plugged and abandoned in 1990.

Over the past 10 years, Calpine has been injecting up to 20 million gallons of reclaimed wastewater per day from Santa Rosa and Lake County into the underground steam reservoir to produce additional steam and manage the entire field as a whole. This injection process is what makes it possible to revisit abandoned well sites and bring them back online. ...

The Geysers is the single largest geothermal operation in the world, producing up to 725 megawatts of green energy around the clock — enough electricity to power the entire city of San Francisco.

Today this 45-square mile steam field, with its 330 steam wells and 75 injection wells, represents 41 percent of overall geothermal generation in the U.S.