Energy
Geothermal Energy - Upload Knowledge
Geothermal technology
uses heat from underground to either warm the air in buildings, warm buildings’
water supplies, or heat-up water in order to generate electricity.
Generally, a pipe runs into the ground cycling a liquid to be heated and brought
back to where it’s used in a building or at a power plant. A similar
method actually extracts hot water from between the pores of rock underground
and brings it to the surface where it’s used for heat or electricity generation,
and then sent back into the ground to have its temperature restored, while new
hot ground water is taken to continue the process. If you want a really
easy-to-understand guide to geothermal concepts, check out
this page by
the California Energy
Commission’s Energy Quest™. For a more thorough guide, check out
this page by the Union of Concerned Scientists.
Geothermal is a vast renewable energy source, and the
REPP reports that it has 50,000 times the energy potential compared to all
the fossil fuel resources in the world, and even if only a fraction of it could
be used, a great portion of our energy needs would be met. And not only is
geothermal abundant, but it is very clean, producing hardly any air pollutants
compared to fossil fuels. According to the
DOE,
direct use of geothermal energy is also significantly cheaper than fossil fuels,
and can result in savings of as much as 80%.
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If you’re interested in a detailed analysis of the future potential for
geothermal energy, check out the
2007 report compiled by a panel led by the Massachusetts Institute of
Technology, or listen to an
interview
with Jefferson Tester, who chaired the preparation of the report.
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The
Geo-Heat Center explains
how different areas of the country have varying levels of heat that are within
reach beneath the earth’s surface. The high temperature areas can be used
to heat water in order to make steam for
electricity
generation at geothermal power plants. Moderate temperature areas can
be used for
direct
use technology which uses water to directly heat buildings or industrial
processes that require heat. The mild heat areas are generally only used
for
ground source
heat pumps, which transfer heat from underground in order to warm buildings
in the winter, and in the summer they transfer the cooler temperatures from
underground into the hotter buildings to cool them. For a visual of these
different heat areas, check out
this
map from the Geo-Heat Center. Notice that although high and moderate
temperature resources are mostly in the western states, all of the United States
has access to the earth’s mild heat resources which can be used by
ground source heat
pumps for any building.
If you want to learn more about the different techniques used to generate
electricity from the high temperature geothermal sources, check out
this page from the REPP. But, if you are more of a visual learner,
check out
this excellent
tour of geothermal power plant technology on the Geothermal Resources
Council website, or check out the
DOE’s
animation on how an Enhanced Geothermal System (EGS) works. For more
about direct-use technology that comes from the moderate heat sources, check out
this page
from the DOE. For visual learners who want to learn more about
ground-source heat pumps that come from mild temperature areas or shallow
applications, watch the short
heating & cooling systems video by
GeoExchange.org.
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If you still can’t find the educational material you’re looking for, check out
the Department of Energy’s list of
other
educational resources or the Geo-Heat Center’s
list of links.
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Pros--
Replacing fossil fuels with geothermal energy can have a profound positive
impact on the environment. According to
Earth Source,
if every school in the U.S. replaced their HVAC system with a GeoExchange
heat-pump system, it would have the same effect as cutting out 61 million
barrels of oil a year or planting 8-million acres of trees. The
electricity generating geothermal technologies are also better for the
environment. According to the
Union of Concerned Scientists, geothermal electricity generation releases
only about 5 percent of the carbon dioxide released in a fossil-fuel powered
plant per kilowatt-hour.
Also, geothermal heat pump systems produce virtually no combustion or indoor air
pollutants according to
Geothermal Heat Pump Consortium, so they are better for your health too.
Another benefit is that geothermal heat pump systems are 48% more efficient than
gas furnaces, and 75% more efficient than oil furnaces according to the
EPA. Greater efficiency and a cheaper
energy source equals savings on your bill too! Not to mention, they also
cost less to operate and maintain according to the
Geothermal Heat Pump Consortium.
Geothermal also has the exciting potential to provide both heat and electricity
generation together in some systems.
Cons—
One of the biggest disadvantages of geothermal technology is simply the fact
that it has been largely ignored as a viable and cost-effective
electricity-generating source, and therefore its enormous potential has not been
fully developed. The
2007 report by the MIT-led panel noted how in order for
Enhanced
Geothermal Systems to become a competitive player in the energy market,
$300-$400 million will need to be invested over the next 15 years. With
government research and development assistance heavily funding other sectors,
such as biomass, large-scale geothermal development is struggling to gain an
economic foothold.
There are also some environmental concerns with geothermal technology, most
notably air and water pollution. The
Union of Concerned Scientists explains that
open-loop systems can produce solid waste and fumes that are harmful to
humans, as well as potentially put a strain on the underground water supply.
However, the
closed-loop systems avoid these hazards altogether because they circulate a
liquid that stays safely in the pipes, and does not deplete the underground
water supply.
Unfortunately,
carbon
dioxide makes up roughly 10 percent of the gases trapped in geothermal
sources, and according to the
Union of Concerned Scientists, that
carbon
dioxide can be released at hydrothermal power plants. However, the
amount of carbon dioxide emitted is only 5% of the amount at a coal or
oil-powered plant. Another concern is that geothermal development at
geysers releases steam with hydrogen sulfide, ammonia, and methane, in addition
to the carbon dioxide. When these emissions are reduced or when the steam
condenses, a new problem of toxic sludge develops, and the toxic sludge is
expensive to dispose. However, this sludge can be pumped back into the
ground to avoid problems if it is pumped deep enough to be below the underground
water supply.
The final challenge for geothermal technology is that many of the prime
hydrothermal resources are located near protected parks or in unspoiled
wilderness areas. Hopefully numerous other viable spots will be developed
and reasonable compromises can be made, because according to the
DOE, there
are 9,000 thermal wells and springs in the 10 western states and an additional
900 low to moderate resource spots.