Turbine
Generator
Load
Production
well
Injection
well
Rock layers
(a)
Flash
Load
tank
Turbine
Generator
Rock layers
Production
Injection
well
well
(b)
FiGUre 3.3 (See color insert.) Three methods of recovering geothermal energy: (a) dry steam,
(b) flash steam. (Adapted from Union of Concerned Scientists, How Geothermal Energy Works,
Union of Concerned Scientists, Cambridge, MA, 2012; National Renewable Energy Laboratory.
Planta Solar 20. http://www.nrel.gov/csp/solarpaces/project_detail.cfm/projectID=39.)
39
Energy Recovery by Benign Hydrothermal Processes
very hot water is depressurized or “flashed” into steam that can then be used to drive
turbine. In the third “binary system” approach, the hot water is passed through a heat
exchanger, where it heats a second fluid, such as isobutene, in a closed loop. The isobutene boils at a lower temperature than water, so it is more easily converted into steam
to run the turbine. This method is schematically described in Figure 3.3c [14].