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The Best is in the West
While it is true that hot springs exist in many places east of the Great
Plains—Hot Springs National Park in Arkansas is one of the best examples—geothermal
energy is far more abundant in the western states, and that is where most
of the U.S. geothermal development is taking place. The western concentration
of the geothermal resources in the U.S. results from the “youth” of the
landscape, indicated in part by the abundance of mountains and faults located
there. While most people fearfully link faults only to earthquakes, when
it comes to geothermal energy, they are our “friends”. Faults are welcome
because they provide pathways for hot waters to reach closer to the surface.
Without these faults, it could be too deep to tap. In some places such as
Hawaii and Iceland, faults are numerous and volcanic activity evident. These
are the most attractive places for geothermal power plants because the resource
is high temperature and close to the surface. The same places are
of course riskier locales to install geothermal power plants, yet generating
stations do exist in both locations.
Within the 48 conterminous states, the most concentrated geothermal activity
is in Yellowstone National Park. While this huge geothermal resource is
a tempting development target for developments, it is off-limits. If not
there, where? Just like people who prospect for gold, those looking for
geothermal “nuggets” go where it is most obvious right on the surface.
Such places might display, for example, hot springs, fumaroles, boiling
mud, the rotten-egg odor of hydrogen sulfide, and occasionally even a small
geyser. Again these places tend to concentrate in volcanic areas—such as
the Cascade Mountains—and near faults.
Figure 14 - This Geothermal Resource Potential map was produced by the
Southern Methodist University Geothermal Laboratory Source: http://www.smu.edu/geothermal/georesou/georesourcesmap.htm
The longest and best-known fault in North America
is the San Andreas in California, and—no surprise—there are many geothermal
energy sites in its vicinity, starting in the southern part of the state
in the Imperial Valley. The Imperial Valley is the landward extension of the
Gulf of California, and the San Andreas Fault is responsible for separating
Baja California from the rest of Mexico. The Valley, located about
50 miles west of Yuma, Arizona, is an agricultural oasis producing about
$1.25 billion per year. But beneath the fields of alfalfa and onions
lay 20-30,000 megawatts of generating capacity, enough to meet the electricity
needs of most of California’s residents. Further to the north are several
other attractive sites, particularly near Coso Hot Springs and Mammoth
Hot Springs. Both host geothermal power plants. Nothing, however,
can match the largest geothermal development in the world—The Geysers—about
90 miles north of San Francisco, where almost 2,000 MW of capacity is installed.
State
|
Location
|
#Units
|
MW Rating
|
2000 MW Actual
|
CA
|
The Geysers
|
27
|
1,989
|
1,137
|
|
East Mesa
|
7
|
105.4
|
105.4
|
|
Heber
|
13
|
80.0
|
80.0
|
|
Salton Sea
|
14
|
347
|
347.3
|
|
Honey Lake
|
5
|
4.3
|
4.3
|
|
Coso
|
9
|
260
|
260
|
|
Casa Diablo
|
8
|
27
|
27
|
NV
|
Beowawe
|
1
|
16
|
16
|
|
Brady H.S
|
3
|
21.1
|
21.1
|
|
Desert Peak
|
2
|
8.7
|
8.7
|
|
Dixie Valley
|
1
|
66
|
66
|
|
Empire
|
4
|
3.6
|
3.6
|
|
Soda Lake
|
9
|
16.6
|
16.6
|
|
Steamboat
|
13
|
35.1
|
35.1
|
|
Stillwater
|
14
|
13.0
|
13.0
|
|
Wabuska
|
2
|
1.2
|
1.2
|
|
Steamboat Hills
|
1
|
14.4
|
14.4
|
UT
|
Cove Fort
|
7
|
31
|
31
|
HI
|
Puna
|
1
|
25
|
25
|
TOTAL
|
|
141
|
3,064.4
|
2,212.4
|
Figure 16 - There is enough geothermal energy in the US to satisfy
the needs of over 15 million people. Source: http://www.geo-energy.org
|
Figure 15 - A more detailed map of the geothermal regions of the continental
western United States
|
In total, California has 2441 MW installed and 340 MW planned. Outside
California, geothermal resources are also particularly attractive in Idaho,
Utah and Nevada. Virtually everywhere in the Silver State has potential for
geothermal development. The reason is simple. Nevada is
geologically new and heavily faulted; in other words, not only is there ample
heat underground, but there are many ways for it to move toward the surface.
Currently, Nevada has about 200 MWe installed, and Utah has another 31 MWe.
Another western state, Hawaii, has 25 MW installed. The present US installed
capacity for electric power generation is 3,064 MWe, but with only 2,212
MWe in operation due to reduction at The Geysers geothermal field in California.
These installations produce approximately16,000,000 MWh per year. Putting
this into perspective, a 2,000 sq ft house in the Phoenix area requires
about 20-25 MWh per year. Using this figure, geothermal generation in the
U.S. provides enough electricity for about 650,000 Arizona homes, more than
the population of Phoenix. The potential electrical generating capacity
for the U.S. is almost 19,000, using enhanced technology.
Figure 17 - The potential US electrical generating capacity is almost
19,000 megawatts, enough for more than 15 million people.
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