The Northern California Power Agency (NCPA) Geyser is a publicly operated facility, generating power from geothermal wells on site. Since the mid-1980s, NCPA has operated two geothermal power plants in Sonoma and Lake counties, California, that have produced more than 27 million megawatt-hours of electricity for its 11 members/owners. The plants consist of 77 geothermal wells, two 110-MW power plants (with two 55-MW generating units each) and associated steam pipeline facilities.
The goal of the modernization was to provide a complete control package using pre-designed integration drawings, with minimal installation challenges. Striving to permit ease of operation and ease of maintenance, Siemens Energy was tasked with updating the first of two plants, focusing on the BoP, generator and turbine control systems to a state-of-the art DCS system, which can easily be expanded into a plantwide DCS system in the future. Another goal of the modernization was to improve the control of the steam valves with a high pressure oil system and closed loop servo control steam valves.