Geothermal energy is a renewable, reliable energy source with a wide
array of uses. In the most basic terms, it is harvesting the
internal heat of the Earth for any number of applications, including
heating, cooling, electrical generation, agriculture, aquaculture,
balneology (hot baths, health spas), and industrial uses to name a
few. Although geothermal energy has been used for the last 10,000
years, it is only since the end of WWII that it has been widely seen as
a competitive alternative to other energy sources.
(http://iga.igg.cnr.it/geo/geoenergy.php (International Geothermal
Association))
Quite literally, “Geo" means of the Earth, and
“Thermal" comes from the Greek “Therine", meaning heat.
(http://geothermal.id.doe.gov/what-is.shtml) All geothermal
energy uses exploit the heat naturally contained within the Earth to
perform some task. There are two basic types of geothermal
energy, high temperature and low temperature. The high
temperature geothermal areas have temperatures that exceed 150 degrees
Centigrade. These are the most useful for electricity generation
on the industrial level.
(http://geothermal.id.doe.gov/what-is.shtml)
Geothermal energy is a natural part of the energy
flow within the Earth’s depths. Generally speaking, the further
down one drills, the hotter the temperatures. Most of the
commercial-grade production geothermal energy is harvested along
localized “geothermal systems", where the heat flow is near enough to
the surface that hot water or steam is able to rise either to the
surface, or to depths that we can reach by drilling. Many of
these regions occur within the “ring of fire", a ring of geothermal
sites. (http://geothermal.id.doe.gov/what-is.shtml, Ristinen, Kraushaar
158-160)
There are three basic types of geothermal
electricity plants. Selection of one type or another is based
mostly on the geothermal resources readily available.
(http://geothermal.id.doe.gov/what-is.shtml)
In areas where steam can be directly harvested, a
Dry Steam generation plant is often used. This is the simplest
and most direct method of electrical generation from a geothermal
resource. It uses rising steam from a well to push a
turbine. The turbine in turn generates electricity. After
the steam has pushed the turbine, it is then sent through a series of
cooling units that allow air and water vapor to escape into the
atmosphere, and return cooled water back to the geothermal reservoir.
(http://geothermal.id.doe.gov/what-is.shtml)
The most common type of electrical generation is
done through Flash Steam plants, where hot liquid (360+ degrees
Fahrenheit) is drawn from a geothermal reservoir. The liquid is
pumped at high pressure, and then allowed to suddenly drop pressure,
resulting in the conversion of some of the water into steam that can
generate electricity. This steam turns a turbine, much like that
in a Dry Steam plant, and the remaining water and condensed vapor are
returned to the well. (http://geothermal.id.doe.gov/what-is.shtml)
A third alternative for electricity generation is
the Binary Cycle plant, where a working fluid is heated with the
extracted hot liquid. This is useful in areas where the
temperature might not be appropriate for a Flash Steam plant. By
using a working liquid with a lower boiling temperature than water,
more steam is produced to generate power. In addition, the hot
liquid from the Earth never actually comes in contact with the turbine,
as it’s heat is simply transferred through a heat exchange unit.
These facilities can operate at temperatures as low as 225 degrees
Fahrenheit. (http://geothermal.id.doe.gov/what-is.shtml)
Electrical generation is not the only use for
geothermal energy. Heat Pump technology has brought geothermal
energy into the home, as an inexpensive source of heating and
cooling. These heat pumps don’t require intensely hot reservoirs,
or dry steam, but rather run much like a refrigerator with pipes
extending either out or down in a loop below the frost line. This
technology is expandable to much of the world, and is available right
in one’s backyard. (http://geothermal.marin.org/pwrheat.html#Q2)
There are several other direct uses of geothermal
energy. Extracted hot water can be used in both agriculture to
extend the growing season, and aquaculture, to shorten the time to grow
fish and shrimp. Industrial uses like pasteurizing milk, and
washing wool have been around for decades. A town in Oregon has
even begun using hot geothermal water to keep their sidewalks and roads
from freezing. (http://geothermal.marin.org/pwrheat.html#Q2)
Geothermal energy has enjoyed a wide array of past
uses. It has been documented as an energy source for over 10,000
years. The Romans used it to heat buildings and treat eye and
skin diseases. The Native Americans have used the hot waters to
cook and for medical reasons, and the France has used it to heat over
200,000 homes. (http://geothermal.marin.org/pwrheat.html#Q2)
Geothermal energy uses range from localized heating
and baths, to large-scale energy production. There is a varying
amount of infrastructure based upon the use for geothermal energy to be
efficiently harvested. According to the multi-disciplinary
engineering group, Mott MacDonald, radial heating can be n efficient
source of energy that is built into new homes and buildings. In
terms of electrical generation, much of the distribution infrastructure
exists already, the only piece remaining are the production wells and
turbine used to generate the electricity. The problem is that the
geothermal resources are often located in inaccessible areas, or areas
that are too far from the main power grid to be efficient in electrical
production. (MacDonald 5,
http://geothermal.marin.org/pwrheat.html#Q2)
Worldwide energy production from geothermal
reservoirs has grown to approximately 7,000 MW, with 2,700 of those
being produced in the U.S. This represents a very small
percentage of the overall worldwide electrical production, but
geothermal energy is rapidly expanding, some predict almost 500%
gains. Of course, many of the uses have nothing to do with
electricity, and unlike electrical production, heating and cooling are
not limited by the availability of high temperature wells.
(http://geothermal.marin.org/pwrheat.html#Q2)
Geothermal energy is a 10,000 year old source that
has a wide-array of uses. It will continue to be a big player in
the world’s hunger for energy. As the efficiency and uses
continue to grow, so too will the technology that helps provide the end
user with clean reliable, and if used in a sustainable manor, renewable
energy.
|
tweet this!
