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#Post#: 47--------------------------------------------------
Renawable Energy: Geothermal Spotlight
By: BPleat Date: August 23, 2012, 12:36 am
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Renawable Energy: Geothermal Spotlight
Ben Pleat ‘13
Over the past decade, and perhaps for even longer, renewable
energy has seen a tremendous increase in its share of total
power production in the United States. Although petroleum, coal,
and natural gas plants dominate over 83% of the United States’
yearly power production, sustainability itself contributes to
the inevitability of the trend toward renewable sources.
This sector commonly labeled under the comprehensive hood of
‘renewable energy’ actually consists of over ten discrete
sources, including solar, wind, hydroelectric, and geothermal.
In this article, we will focus on geothermal energy, a highly
underdeveloped energy source that shows great potential for
power production.
First, we must clearly establish exactly what geothermal energy
is and how plants function. Geothermal energy, in essence, uses
the earth’s natural heat as a way to harness energy for power
production. Several kilometers below earth’s crust, the
temperature ranges over 700 degrees Fahrenheit. This natural
heat, coupled with the presence of a deep-water reservoir,
represents a ‘geothermal system,’ which can be tapped for power
production. A geothermal power plant functions much like a
nuclear plant or a coal plant in that the process of turning a
turbine is what produces the electricity (when combined with an
electric generator). The steam that exits wells in geothermal
systems, in this case, is actually what turns the turbine.
The three types of plants include dry steam, flash cycle, and
binary cycle. In the rare case of a dry steam power plant, steam
is directly derived from the system. In the flash cycle plants,
high-temperature fluids are pumped into pressurized tanks that
allow some of the fluids to vaporize into steam. A binary cycle
plant, unlike the two aforementioned types, uses the heated
fluids to heat a secondary substance with a substantially lower
boiling point (e.g. butane), which is then used to turn the
turbine. This type of plant is especially useful, as the
geothermal systems can be lower in temperature (below 300
degrees Fahrenheit), in turn allowing such plants to be located
in a wider assortment of regions.
Currently, most geothermal power production is concentrated in
the western United States, such as in Nevada, California, and
Utah. Additionally, several plants have been constructed in
Hawaii and Alaska.
The benefits of geothermal energy point toward a clean and
sustainable alternative to a fossil fuel-thirsty global economy.
Geothermal plants produce under a sixth of the carbon dioxide as
natural gas plants, as well as little to no nitrous oxide or
sulfur-containing gases that contribute to acid rain. Moreover,
binary plants operate under a closed cycle, which means that
virtually the only emission is water vapor. In terms of cost,
geothermal energy currently is at $0.05 per kWh, much cheaper
than solar and natural gas ($0.20 and $0.11, respectively).
Despite the apparent advantages of geothermal, it still only
accounts for 0.4% of electricity in the U.S., as reported by the
U.S. Energy Information Administration. The report from the EIA
also cited that geothermal plants compose 5% of California’s
total annual power production, with an overall increase of 10%
from 2008.
The question still remains: why does geothermal energy still
constitute such a small percentage of the total power
production? Quite simply put, the answer to this question is
multidimensional. High technology costs and the expenses of well
drilling cause geothermal projects to be exposed to high risk.
Unsuccessful projects and drilling attempts could hinder future
exploratory undertakings for years, all contributing to further
setbacks. Furthermore, locating viable locations of economic
geothermal systems also precludes geothermal energy from
reaching its full potential.
Despite such impediments, geothermal energy represents a
promising alternative to other forms of energy. According to a
study conducted by the Department of Energy, geothermal power
could theoretically provide over 60,000 times the Unites States’
yearly power consumption. Although such a figure is not
attainable in the near future, the California Energy Commission
estimates that only 10% of geothermal resources in the state
have been brought to market.
In conclusion, geothermal energy has proven itself to be a
highly favorable choice as we progress and as new technology is
introduced. Google.org recently made a $4 million investment
into enhanced geothermal systems (EGS), which use a process
known as ‘hydraulic stimulation’ to create geothermal systems.
For regions that lack fracture permeability, natural convective
heat flow, and other factors that commonly constrain geothermal
plant development, EGS represents an exciting new development
that could catapult this form of renewable energy to higher
portions of the annual power production in the U.S.
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