Geothermal power is heat taken from the Earth’s core and used to heat water or another fluid to a specific temperature to turn a turbine generator, producing electricity. The water or other fluid is then cooled and returned back to the heat source (Earth’s core). There are three different types of geothermal power stations: dry steam, flash steam and binary cycle. Dry steam power plants take steam at temperatures of 150 degrees Celsius or greater directly from the source to turn generators. Flash steam power plants pull high pressure hot water (at temperatures greater than 180 degrees Celsius) into low pressure water tanks. The resulting “flashed” steam is used to turn the turbines. Binary cycle power plants do not require water as hot as dry-steam or flashed-steam plants. Moderate-temperatured water is simply passed over a secondary fluid with a boiling point lower than water. When the hot water passes over it, the secondary fluid flashes and vaporizes – turning the turbines. EETS has experience working with the electrical design for dry and flash steam geothermal power plants.

Spotlight: Geothermal Projects

Calpine Sonoma Unit #3 (formerly SMUD Geothermal)
Sonoma County, California

The Sonoma Power Plant is owned and operated by Calpine and consists of a dry steam geothermal power plant. This plant generates a baseload of 42MW and uses Mitsubishi steam turbines.

EETS engineers worked on the following geothermal modifications for Calpine:

  • Modifications and additions for 21kV service to City of Santa Rosa Wastewater Treatment Plant
    • 30MVA load-tap changing 13.8kV:21kVA
    • 4000 amp non-seg phase bus tap
  • 13.8kV and 21kV breakers, disconnects, structures and footings
    • Protective relaying and metering additions and modifications

Calpine Geysers Geothermal Units #1, #13, #14, #18, #19
Sonoma and Lake Counties, California

Calpine’s Geyers Geothermal Units together comprise the largest complex of geothermal plants in the world, producing a net generating capacity of 725MW of electricity. EETS engineers worked on the design and modifications for five of the fifteen power plants including the design of microprocessor protective relay upgrades for the 230kV substation and unit generator protection. These five plants represent over 300MW of capacity.