Page 369 - Handbook of Energy Engineering Calculations
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drilled wells that range in depth from 4000 to 6000 ft (1219 to 1829 m). The
binary fluid is vaporized in a heat exchanger and led to a turbine coupled to
an electric generator. (d) In a combined-cycle geothermal plant, Fig. 1d, the
overall thermal efficiency is higher, just as in fossil-fueled combined-cycle
plants. Brine and steam enter a separator with steam leaving the separator and
being piped to a turbine for production of electricity. Brine leaving the
separator enters a heat exchanger where it generates steam in a secondary
working fluid for a turbine that produces electricity.
FIGURE 1 Geothermal power cycles. T = turbine. G = generator. C
= condenser. S = separator. E = heal exchanger.
When a geothermal well produces brine or hot water at less than 250°F
(121°C), steam power generation of electricity is not normally considered
economically possible. But the heated fluid can be used for services such as
district heating, food processing, industrial process heating, and so on.
