Page 368 - Handbook of Energy Engineering Calculations

SECTION 9

GEOTHERMAL ENERGY ENGINEERING

Geothermal Calculation Parameters

Cycle Analysis of a Vapor-Dominated Geothermal Steam Power
Plant

Geothermal and Biomass Power-Generation Analyses

Flashed-Steam Geothermal Power Plant Analysis

GEOTHERMAL CALCULATION PARAMETERS

Geothermal energy is considered to be green, semi-renewable,* free of
greenhouse gases (GHGs), and an excellent alternative to coal, oil, gas, and
similar fossil-fuel energy sources. The major disadvantage of geothermal
generation of power is that the energy sources are often great distances from

the power users. But as transmission lines are extended this disadvantage
decreases, or disappears.
The steam Rankine cycle used in fossil-fueled power plants is also used in
geothermal power plants, as reported by Kenneth A. Phair in the Marks

reference cited later. Four types of cycles can be used in geothermal plants,
Fig. 1. These cycles are: (a) Direct steam cycle, Fig. la, in which steam is
delivered directly from in-ground production wells to the steam turbine;
steam leaving the turbine passes to a condenser where it is converted to water

for return to the well; (b) In a flash-steam cycle, Fig. lb, brine from the well,
or a mixture of brine and steam, is delivered to a flash tank in which flash
steam is produced that is delivered to the turbine for electric power
generation. (c) Many geothermal generating plants today are binary-cycle,

Fig. lc. The plant uses hot water, usually at 275°F to 300°F (135°C to 149°C)
to heat a binary fluid (isobutene or isopentane). This hot water comes from