Geothermal handbook: PlanninG and Financing power Generation t e c h n I c a L r e p o r t 2 / 2

F I g u r E 1 . 1 3
Geothermal Power Generation by Various Technologies, 2010 (% of total 67 TWh)
Source | Adaptation from Bertani 2010.
Double Flash 
21%
Dry Steam 
24%
Back Pressure
4%
Single Flash
42%
Binary
9%
Single or double Flash Plants: Condensing units or Conventional Steam Cycle
Commonly built in sizes from 25 to 60 MWe, a “condensing unit” (also called a conventional steam 
cycle) is the standard technology used to generate power from fluid or steam with temperatures above 
200°C. In Figure 1.14, the flow of high temperature fluids is indicated in red and the flow of the cooling 
water in blue. 
The most common version of the condensing unit is the single flash steam plant, usually the most 
economical choice for high-enthalpy liquid dominated resources. The hot water or liquid vapor mixture 
coming from the wellhead is directed into a separator, where the steam is separated from the liquid. 
The steam is expanded through a turbine and then usually reinjected, together with the separated 
brine, back into the reservoir. The brine could, however, be used by a “bottoming unit”
14
or in another 
application, such as heating, cooling, or multiple use.
14
Bottoming units use the residual heat from the main power plant to generate additional power.

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