Binary cycle power

The temperature in the core of the Earth—due to the decay of radioactive isotopes—is on the order of 4,000°C, the temperature of the lava of volcanoes is about 1,200°C, and the temperature of thermal springs can reach 350°C. If the groundwater temperature exceeds 150°C, flash steam power plants can be built, and if it is between 100 and 150°C, binary cycle power plants can be operated. 

In this demonstration plant, the boiler feedwater can be preheated by geothermal heat if available. Depending on the availability and temperature of the geothermal heat in the area, the geothermal plant s design would vary. If the groundwater temperature exceeds 150°C (302°F), a "flash steam" power plant would be used, and if it is between 100 and 150°C (212 and 302°F), a "binary cycle" power plant would be used. 

The flashed steam method is less efficient and its requirements for steam properties—cleanliness, high temperature, and high pressure— are usually unavailable in most geothermal fields. The situation is different with the binary cycle system, which is quite efficient and widely used. This wet system involves the transfer of heat from the hot well stream into a more manageable boiling fluid to generate power through a turboexpander. 

Fig. 4. Simplified schematics of binary cycle-type power plant. (Modified from Hudson 1998).

Flash Steam Generation The most common type of hydroelectric power generation technique. Flash steam describes a system where a high temperature geothermal steam source can be used to directly drive a turbine. Also see Binary Cycle Generation. ... 

Geothermal Electric Power Generation Electricity derived from heat found under the earth s surface. Also see Flash Steam Generation, Binary Cycle Generation and Hot Dry Rock Geothermal Energy Technology (HDR). ... 

The characteristics of the hydrothermal resource determine the power cycle of the geothermal power plant. A resource that produces dry steam uses a direct steam cycle. A power plant for a liquid-dominated resource with a temperature above 165°C typically uses a flash steam cycle. For liquid-dominated resources with temperatures below 165°C, a binary cycle is the best choice for power generation. Power plants on liquid-dominated resources often benefit from combined cycles, using both flash and binary energy-conversion cycles. 

Fig. 6 Binary cycle geothermal power plant. (View this art in color at WWW. dekker. com.)...

There are two main types of geothermal power plants flash steam type and binary cycle. The flash steam plant is driven by pressurized, hot (300-700°F) steam brought up from depth of as much as more than 10,000 feet. When this pressure is reduced at the surface by about a third or so, the water flashes —explosively boils—into steam which drives the turbine and generator. Binary plants are driven... 

Binary Cycle - Combination of two power plant turbine cycles utilizing two different working fluids for power production. The waste heat from the first turbine cycle provides the heat energy for the operation of the second turbine, thus providing higher overall system efficiencies. 

Cryotrons are essentially low power computer elements, and are used predominantly in digital computers to perform binary switching operations. However, cryotrons can be used as rectifiers by feeding in an ac signal and quenching it on alternate half-cycles with an appropriate solenoid control current (see Fig. 2). 

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