Page 167 - Geothermal Energy Renewable Energy and The Environment

9 Generating Power Using

Geothermal Resources

The production of electricity using geothermal energy employs technology that is fundamentally
indistinguishable from that at most other electricity generating facilities. Specifically, an elec-
trical generator is powered by a turbine that converts thermal or kinetic energy into electricity.
However, in two important respects geothermal power production is unique when compared to
other power production methods. First, when compared to power generating technologies that
supply baseload power, such as fossil fueled power plants, biomass reactors, or nuclear reactors,
there is no fuel cycle required to generate heat since the heat already exists within the Earth.
Second, when compared to other renewable energy technologies that do not require a fuel cycle
for heat generation, such as wind, solar, tidal or ocean wave technologies, geothermal is not
intermittent and provides true baseload capability at a reliability that consistently exceeds 90%.
The remainder of this chapter addresses the physics of power generation as it relates to geo-
thermal power production, and design issues that are specific to particular types of geothermal
resources. For a detailed discussion of geothermal power plant design see the presentation by
DiPippo (2008).

The hIsTory oF GeoThermal power prodUcTIon
The first production of electricity from geothermal steam took place in Larderello, Italy in 1904.
Larderello is in a region of Italy with substantial recent volcanic activity, including explosive steam
eruptions that occurred as recently as the late 1200s. With the growth of the Industrial Revolution,
interest in exploiting the geothermal resource of the area grew, beginning with the direct use of
steam at Larderello to support a local chemical separation industry. However, it was the innovative
application of a small steam generator powered by the Larderello geothermal system that gave birth
to the geothermal power industry.
The small steam generator that was first used in Larderello lighted four light bulbs in a dem-
onstration project conceived by Prince Piero Ginori Conti. Seven years later, in 1911, industrial
scale production of geothermal power was brought online and used in-house for the commercial
chemical applications that were being pursued at the time. In 1916, a 2500 kW generating capac-
ity was brought online to provide electricity commercially to the local communities (Bolton
2009). Larderello remained the world’s only geothermal power plant of industrial scale until
the 1950s when New Zealand brought online its first geothermal power plant. Between the early
1950s and 1963, New Zealand began generating electricity at Wairakei, with an installed generat-
ing capacity of more than 190 MW of electrical power (Bolton 2009). Meanwhile, at The Geysers
in California a utility company, Pacific Gas and Electric, installed a generator with a capacity
of approximately 12 MW (Smith, Beall, and Stark 2000). Since that time, the global growth in
geothermal power production has been rapid, as documented in Figure 9.1. As of early 2009,
the global annual growth rate for installed geothermal power generating capacity was approxi-
mately 10%. Table 9.1 lists the global geothermal power generation capability for 1995, 2000,
and 2007.

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