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GEOTHERMAL ENERGY
Unlike
most of the other sources of renewable energy,
geothermal energy does not derive directly or indirectly
from the sun. The ultimate source of the earth's
internal heat (estimated at six thousand degrees Celsius
at the core) is still under debate, but the most likely
explanation at this point is latent radioactive decay
within the earth itself. Like hydrological power,
geothermal energy production has its roots in our
distant past; ancient Romans and Chinese frequently
described the use of hot springs for medicinal or
recreational purposes. In seismically active areas, such
as Iceland, steam and heat from geysers has long been
used as a source of energy. Current geothermal
applications use water that has been heated beneath the
earth's surface, as well as heat from the ground itself,
and account for more renewable energy than any source
except hydroelectric and biomass.
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There are several methodologies currently used to
harness geothermal energy. The first is known as
direct-source, and refers to using this latent energy
directly. This is the method used by the ancients and
modern resorts, such as those in Bath, England or Hot
Springs, Arkansas. High temperature ground-water is
pumped directly into radiators or water pipes, and is
used to heat baths, saunas, or even industrial
complexes. Of course, this requires an easily accessible
high-temperature water source, and is therefore suitable
only for certain geographical regions.
A ground source heat pump (a device used to transport
heat from one location to another) is a potentially more
wide-spread application of geothermal power. The idea of
using a heat pump to draw energy from the ground was
first suggested in 1912, and successfully demonstrated
in the 1940s. A heat pump installed in a home or
business can be used to heat during the winter, and as a
heat sink to cool in the summer. They are relatively
easy to install , and can be used almost anywhere. Some
estimates suggest that over forty thousand heat pumps
are installed annually world-wide.
A third use is geothermal electrical generation plants.
In particular, steam from a geyser or other underground
source is used to turn a turbine, in much the same way a
a traditional fossil-fueled power generation plant
operates, but without the use of incineration.
Alternatively, a hole is drilled down to an area of “hot
rocks,” and cold water is pumped in. Steam is created
when the cold water hits the rocks, and that steam is
used for the turbines. Unlike ground source heat pumps,
geothermal electrical generation plants need to be built
near the fault lines of tectonic plates or seismically
active areas to have access to sufficient energy
reserves, meaning that some of the best sites may be
uncomfortably close to volcanoes or other magma flows.
There has been some evidence that drilling near fault
lines can trigger seismic activity, such as earthquakes.
Some potential plants have even been forced to abandon
construction due to unstable tectonics. There is also an
increase in the release of greenhouse gases from
drilling into air pockets, though considerably less than
from burning fossil fuels. Additionally, some long-term
electrical plants, such as in California and New
Zealand, have shown a decrease in productive capacity
since their implementation. This is most likely due to
water being removed from the natural system faster than
it is replaced. Recent tests have shown that if water is
re-injected into the system, full capacity can be
restored.
In the United States, geothermal generators currently
produce roughly the same amount of power as four nuclear
power plants. A collection of geothermal plants in
California known as “The Geysers” has been producing
economically viable geothermal electricity since 1960s.
Geothermal electrical generation exceeded fifteen
percent of national power requirements in five
countries: El Salvador, Kenya, Iceland, Philippines, and
Costa Rica, yet his represents a small fraction of the
potential geothermal energy. Unlike dams or wind farms,
geothermal plants require very little land space,
lessening their environmental impacts.
Published by Carol Foss - in the hope that it will make
a difference, however small. |
