Abstract: International Geothermal Development
WRIGHT, PHILLIP M., Energy & Geoscience Institute at the University of Utah; KARL GAWELL, Executive Director, U.S. Geothermal Energy Association
Demand for new electrical generating capacity in developing
countries is at its highest level ever, and with the institution of
market economies in many countries, there are new business
opportunities in geothermal energy. Presently, about 7,000
megawatts of geothermal electrical power
generation is on line in
some 20 countries, including (but not limited to) China, Costa
Rica, El Salvador, Iceland, Indonesia, Italy, Japan, Kenya, Mexico,
New Zealand, Nicaragua, Philippines, Romania, Russia, Thailand,
Turkey, and the United States. The largest operating geothermal
field is The Geysers in the USA, which produces about 1,300
megawatts. By some estimates, as much as 80,000 megawatts of
geothermally generated electrical
power
are available from volcanic
systems in developing countries throughout the world. Indonesia
alone estimates its potential at 19,000 megawatts.
In terms of reliability and sustainability of geothermal
systems, we know that natural geothermal systems have occurred
throughout geologic time, and that a typical lifetime for
geothermal activity around magmatic intrusive centers ranges from a
minimum of perhaps 5,000 years to more than 1,000,000 years.
Geothermal resources are, thus, renewable by any reasonable
definition of the word. We further know that the natural rate of
recharge of geothermal reservoirs varies from a few to more than
1,000 thermal megawatts. The natural recharge rate represents the
minimum rate at which geothermal systems could, in principal, be
produced for tens of thousands of years. In commercial development,
however, geothermal systems are produced at rates that exceed their
natural rates of recharge because to do otherwise would be
uneconomic. Thus, geothermal systems have a finite lifetime during
which they will produce economic electrical power
, although this
lifetime may perhaps be supplemented by a further period during
which they can be used for direct-heat applications that require
lower temperatures.
In operation, geothermal power
generation has proven to be very
reliable. The Larderello field in Italy has produced
power
since
before World War II, the Wairakei field in New Zealand has been
operational since 1958, and The Geysers field in California and
produced
power
since 1960. We can also judge sustainability of
geothermal production from an estimate of the thermal resource
residing in the rocks of the reservoir, where most of the heat is
contained. At The Geysers field in California, the heat content is
estimated as being at least equivalent to that obtained by burning
28 billion barrels of oil or 6.2 billion short tons of coal. Large
geothermal systems are clearly world-class energy resources.
AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah