NCPA Geothermal Plant No. 2

Northern California Power Agency (NCPA) Geothermal Plant No. 2 (NCPA-2) is located near the town of Anderson Springs, in Sonoma County, on federally owned lands in the Geysers Known Geothermal Resource Area (KGRA). The federal lands are administered by the Bureau of Land Management and the Minerals Management Service.

NCPA-2 is currently a 55-megawatt (MW) generating geothermal facility consisting of one 55 MW turbine generators; multiple cell, double flow, mechanically induced draft cooling towers; a transmission switchyard, adjacent to the turbine generator building, containing a 13.8 kilovolt to 230 kV step-up transformer; and, a hydrogen sulfide (H2S) abatement system. Primary treatment will be through a Stretford system, in which H2S is scrubbed from the vent gas stream and catalytically oxidized to elemental sulfur. NCPA will use a hydrogen peroxide secondary H2S abatement system to further reduce emissions to an acceptable level.

NCPA-2 was initially designed and operated as a 110-MW facility comprised of two steam turbines units (units 3 and 4). However, due to the current steam field degradation, there is only enough steam to operate a single 55 MW steam turbine. Unit 4 was modified to accept the reduced new steam conditions. In April 2010, Unit 3 was put into a non-operational state, which is not physically connected to the switchyard or grid. In 2014, NCPA-2 demolished and removed the cooling tower associated with unit 3. The current output for the facility is only 55 MW.

Currently, NCPA-2 is testing the existing fire protection system, including the deficient fire detection alarms, with a plan to make functional changes to the existing fire protection system.