GC: n

CT: Binary Power Plants.
Binary plants, like dry-steam and flash-steam plants, make use of naturally sourced hot steam generated by activity from within the Earth’s core. All geothermal plants convert thermal energy to mechanical energy, then finally to electrical energy.
Binary plants specifically use a second working fluid (hence, “binary”) with a much lower boiling point than water. The binary fluid is operated through a conventional Rankine cycle. Generally, the working fluid is a hydrocarbon such as isopentane, or a refrigerant. The geothermal fluid (predominantly water vapor) and working fluid pass through a heat exchanger, where the working fluid flashes to vapor and drives the turbines. The cooled water vapor is then released back into the underground reservoirs, so the cycle can begin anew. No gas is emitted to the atmosphere, as the binary cycle is a closed system.
The binary cycle can operate with geothermal fluid temperatures ranging from 85°C to 170°C. Depending on the temperatures, different working fluids are selected based on appropriate boiling points. The upper temperature limit is restricted by the working fluids well, as they are generally organic molecules that become thermally instable at higher temperatures. The low temperature limit is restricted by economic and engineering concerns. The heat exchanger size for a given capacity becomes impractical and costly at low temperatures. Parasitic loads that drive the plant also require larger percentages of the output energy.

S: http://large.stanford.edu/courses/2011/ph240/yan2/ (last access: 26 February 2015)

N: 1. binary cycle geothermal plant: The only known operational example of a binary cycle geothermal plant, as distinct from laboratory prototypes, is the small 750 kW (nominal) unit at Paratunka in Kamchatka, USSR.
2. In the fields of Electric Power Stations and Geophysics: binary cycle power installation, binary cycle power plant, Rankin cycle plan.
3. (Binary cycle power plants), sometimes called Rankin cycle plants, consist of two fluid loops, hence the name.

S: 1, 2 & 3. TERMIUMPLUS.

SYN: binary plant

S: http://large.stanford.edu/courses/2011/ph240/yan2/ (last access: 26 February 2015)

CR: flash steam power plant, geothermal power station, geothermal energy, geothermics.