October 21, 2008
Introduction to Earth Science
The Promising Potential of Geothermal Energy
as an Alternative in Energy
By: Alejandro Lerma III and Pooja Shakya
Major world societies are at a point in their existence where their consumption of energy is key
to the how their respective society functions. Without reliable energy, societies cannot thrive nor
can they advance because energy is key to domestic households, productive resources,
consumption of goods and services, technological change, and governing mechanisms. Every
aspect of a society uses energy for both current sustenance and future advancement. Even in the
United States alone, if our forms of energy were lost, our society would collapse; energy is that
method that provides for and propels a society. Although energy is essential for stable, healthy
societies, increasing our use of fossil fuels cannot be the strategy for sustainable development.
Developed and developing countries face a global energy crisis, it is detrimental to continue the
extraction and use of fossil fuels yet it is crucial to find a form of energy that is suitable now and
equally, if not more, effective later. Global energy consumption has continuously increased
since the Industrial Revolution, but that rate of increase has been particularly rapid in recent
decades and shows little signs of slowing (Ghose, 2004). Geothermal energy holds a promise of
becoming an essential alternative form of energy that is both abundant and effective to
supplement our current and future needs. The goal of this paper is to explore the promising
potential of geothermal energy as a feasible alternative energy source. Through the use of
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investigative scientific tools and applicable case studies, the capacity and the need for the power
that lies in geothermal energy will be illustrated.
To begin, scientists believe that geothermal energy - heat from inside the earth - provides a
promising potential to alleviate the current energy crisis and provide a means of sustainable and
more eco-friendly development. Over the past millions of years, large quantities of heat have
been stored in areas where volcanic eruptions or magmatic intrusion has occurred. Engineers are
able to extract large amounts of heat from these areas of high-temperature concentration by
simply pumping out water, which has been heated by these hot, dry rocks through convection
(Wright, 1998). With the development of suitable technology, geothermal energy will be an
important contributor for renewable energy, whose use is expected to increase to 30-80% by
2100 (Wright, 1998).
As for the mechanism by which geothermal energy is produced, it requires a substantial amount
of geological and engineering expertise with proper handling to successfully draw useful energy
out from the earth. The use and utility of geothermal energy is classified into three groups: i)
low temperature (less than 90˚ C), ii) moderate temperature (90˚ C - 150˚ C), iii) and high
temperature (above 150˚ C) each with their respective advantages (Ozgener et.al, 2002). The
high temperature resources are the ones that will be mainly used for electrical power generation.
India for example, has abundant high temperature sources, around 340 hot water springs with
temperatures near boiling points and high bottom temperature holes (140-200˚ C) – which can be
used successfully in the future to meet their growing energy needs (Ghose, 2004). Furthermore,
low and moderate temperatures can be used as direct use and ground-source heat pumps, which
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primarily include space heating and cooling for industry, greenhouses, fish farming, tourism and
health spas (Fridleifsson, 2001). In fact, countries such as China, Japan, USA, and Iceland are
leaders in terms of the installed capacity and used energy produced by geothermal means
(Fridleifsson, 2001; Batchelor, 2005). Other interesting current applications of geothermal
energy include successful models of geothermal district heating in Reykjavik (Iceland) and
space-heating residences and greenhouses in Turkey and Tunisia (Fridleifsson, 2001).
Additionally, in 2000, researchers identified 80 countries with high potential geothermal energy
resources and about 58 countries that were already utilizing geothermal energy.
In terms of benefits, geothermal energy has a broad spectrum of advantageous qualities that have
lend to its appeal. Geothermal energy is not location dependant as fossil fuels are because
geothermal energy is available at a variety of locations where it can be extracted and used.
Geothermal energy is also not weather dependent unlike other renewable means such as: solar,
wind or hydro power.
Most importantly, unlike other renewables, geothermal energy is
constantly available, 24 hours a day, 356 days a year. The ability to have significant amounts of
energy consistently available and not dependant upon other natural factors make the possibilities
for geothermal energy endless. This readily available power could alone potentially provide
100,000 MWe (megawatt electrical) of cost-competitive power in the United States within the
next half century. In terms of pollution, it is incorrect to believe that even with geothermal
power plants no more pollution will be produced because most plants do emit greenhouse gases
in the form of CO2, but the amounts are low. In the United States the average geothermal power
plant emits 27 kg CO2 per MWh (megawatt hour), whereas the average natural gas and coal
plants release 550 and 1,000 kg CO2 per MWh, respectively (Hirtz, 2007). Reduction in carbon
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dioxide emissions is a major benefit of geothermal energy (13-380 g/kWh) in comparison to
natural gas (453 g/kWh), oil (906 g/kWh) or coal (1042 g/kWh). Amongst the four “new”
renewable sources – geothermal, wind, solar and tidal – 70% of the electricity currently
generated is contributed by geothermal energy with only 42% of its total capacity being used.
With further research and development, geothermal energy can be used as a source for both
electricity generation as well as other direct uses like heat pumps for households (Fridleifsson,
2001). Furthermore, it can be stored under proper conditons and due to its relatively lower
current costs (0.5-5 US cents/kWh), it is commercially viable with respect to contemporary
substitutes like biomass (3-20 US cents/kWh) or solar heating (3-20 US cents/kWh)
(Fridleisfsson, 2001).
As with any new form of energy there are potential drawbacks in the use of geothermal energy.
These are not drawbacks in the actual utility of the energy, rather they are drawbacks in the use
and application of the energy. For example with geothermal power plants, the plant must be
located close to the source of geothermal energy because the transport of thermal energy is not
efficient. It is nearly impossible to transport latent heat (and in some cases in the form of steam)
long distances without seriously jeopardizing the quality and amount of heat. Also as discussed
earlier, geothermal power plants do emit greenhouse gases (mainly CO2 in small amounts), but
individual use of geothermal pumps release close to nothing. (Ghose, 2004). In terms of the
quality and energy potential that lies in geothermal energy, the energy per unit mass of
geothermal fluid (hot water/steam) is low compared to oil. Thus the production rates of
geothermal wells must be significantly higher than in oil wells. Geothermal fluids can also
contain other chemicals, mainly nitrogen, carbon dioxide, hydrogen sulfide with trace amounts
of ammonia, mercury, radon and boron (Fridleifsson, 2001). Another major disadvantage and
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one that is currently hindering the proliferation of geothermal energy, is the high-investment cost
for the geothermal wells, pipelines, regulation systems, and power plants (Ozgener et.al, 2004).
Although with enough interest and education about how beneficial geothermal energy is, there
can easily be a push for development.
Geothermal energy certainly has a strong case in terms of becoming not only an alternative
energy source, but an energy source that could revolutionize our energy use.
The global
community is in the midst of an energy crisis and one that cannot simply be solved by increased
use of environmentally harmful fossil fuels. Geothermal energy, with enough development and
utilization, can be a realistic approach to energy that can continue to provide for the societies
demanding it. The science and mechanisms for utility, along with the benefits discussed, make
the case for geothermal energy even more relevant. We can harness the energy from deep in the
earth, and if done correctly, it will be our greatest achievement.
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References
Fridleifsson, I.B. (2001) Geothermal Energy for the Benefit of the People. Renewable and
Sustainable Energy Reviews; 5(3): 299-312
Ghose, M.K. (2004) Environmentally Sustainable Supplies of Energy with Specific Reference to
Geothermal Energy. Energy Sources; 26: 531-539
Hirtz, P.N. (2007) The Hot Renewable: Geothermal Energy. ASTM Standardization News; 4145.
Ozgener, O. (2004) Geothermal Heating Applications. Energy Sources; 26: 353-360.
Wright, P.M. (1998) Geothermal Energy – A Sustainable Resource of Enormous Potential. JOM;
50: 38 -40.
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