Binary cycle

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. 

Figure 4-43. Typical binary cycle used in geothermal plants.

In general, a permutation is the product of m 2 binary cycles, m 3 ternary cycles, m 4 quaternary cycles, etc., all of which are noninteracting. If all of these are factored into (now interacting) binaries, the number is... 

If the geothermal well produces relatively low-temperature fluid (<175 °C), electricity can also be generated by means of binary cycle plants, albeit with low efficiency (see below). The binary system utilizes a secondary working... 

The efficiency tj of conversion of a binary cycle is estimated by a function of the inlet temperature Tt (in °C) (Hudson 1998) ... 

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

Binary Cycle Generation A method of geothermal electricity generation where lower-temperature geothermal sources are tapped. The geothermal steam source is used to heat another liquid that has a lower boiling point, which then drives the turbine. Also see Flash Steam Generation. ... 

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 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 all three cases (flash steam, binary cycle, and GHP installations), after the heat content of the geothermal water is utilized, the spent fluid is reinjected into the underground water reservoir. 

Binary Cycle" Geothermal Heat Pumps (GHPs)... 

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 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. 

The binary cycle shown in Fig. 6 uses isobutane ( -C4Hio) as the binary heat transfer fluid. Heat from... 

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... 

Y. Mori and W. Nakayama, High-Performance Mist Cooled Condensers for Geothermal Binary Cycle Plants, Heat Transfer in Energy Problems, Proc. Jpn-U.S. Joint Sem., Tokyo, pp. 189-196, Sept. 30-Oct. 2,1980. 

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. 

Binary Cycle Geothermal Plants - Binary cycle systems can be used with liquids at temperatures less than 350 F (177 C). In these systems, the hot geothermal liquid vaporizes a secondary working fluid, which then drives a turbine. 

In this section, the risk assessment results for three hazardous materials possibly used in deep geothermal systems and onshore blowouts are presented. The substances are caustic soda used as additive in the drilling phase, benzene and toluene used as working fluids in ORC binary cycle. Results are shown in terms of aggregated indicators for fatalities, injuries, and evacuees. Eurthermore, in case of hazardous substances, fatalities and injuries refer to immediate ones, since no exposure and toxicity in this assessment are taken into account. 

Kohler, S. Saadat, A., 2003. Thermodynamic Modeling of Binary Cycles Looking for Best Case Scenarios. International Geothermal Conference, 2003 Reykjavik, Island. 

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