CAISO’s First Geothermal Plant in 30 Years Comes Online
The first geothermal power plant built in more than three decades within the California Independent System Operator (CAISO) balancing authority has come online. Mammoth Pacific Geothermal, an Ormat Co. subsidiary, declared the 30-MW Casa Diablo IV (CD4) commercially operational on July 20.
CD4 is located on public land two miles east of the Town of Mammoth Lakes in Mono County, California. The project is part of the Mammoth complex, which includes three other plants—one completed in 1985 and two added in 1990—each with a generating capacity of approximately 10 MW. The complex taps into the Long Valley Caldera’s hydrothermal system at a point where the hot water is only a few hundred feet below ground.
CD4 comprises two Ormat Energy Converter (OEC) binary generating units, each 21.2 MW, and vaporizers, turbines, generators, air-cooled condensers, preheaters, pumps and piping, and related ancillary equipment. OEC binary generating units are based on an Organic Rankine Cycle, and work by vaporizing a secondary working fluid (organic, with a low boiling point) that is heated by the geothermal fluid extracted from an underground reservoir.…