SAN JOSE, Calif.-Calpine Corp. has acquired the remaining 45 percent equity interest in the Aidlin geothermal facility from an affiliate of Sumitomo Corp. Located in The Geysers region of northern California, Aidlin is a 20 MW electric generating facility, which provides electricity to Pacific Gas and Electric Co. under a long-term power sales agreement.

Calpine owns and operates 19 of the 21 geothermal power plants at The Geysers. The Calpine plants combined generate approximately 850 MW of electricity-enough energy to supply approximately 850,000 households. Calpine also owns and operates a 14,000-acre steam field operation, where some 360 steam wells and a vast pipeline network supply naturally occurring steam to fuel the company’s geothermal power plants.

“Calpine is committed to the long-term stewardship of The Geysers-one of California’s most valuable natural resources,” said Dennis Gilles, Calpine vice president-geothermal. “This acquisition advances our corporate goal of consolidating The Geysers operations to improve efficiencies and extend resource production.”

“To that end,” added Gilles, “Calpine will continue to pioneer innovative and resource-sustaining programs to ensure Californians can benefit from a clean and reliable renewable energy resource for many years to come.”

Calpine initially acquired a five-percent equity interest in the Aidlin geothermal facility in 1989-representing Calpine’s first megawatt of generation. That interest was increased to fifty-five percent with the acquisition of two other partners’ interests in 1999.

The Geysers, located about 90 miles northeast of San Francisco in Sonoma and Lake counties, is the world’s largest producing geothermal resource, with more than 1,000 MW in production. At The Geysers, wells are drilled to access steam from beneath the earth. The steam is sent via pipelines to turbines, which drive generators to produce electricity.

Power facilities at The Geysers have been in commercial operation for 40 years, and Calpine has been active there since 1987.