Introduction

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Geothermal energy technologies rely on tapping the heat within the earth itself. In this, these technologies differ from most renewable energy technologies which somehow, directly or indirectly, capture solar energy and also that the heat energy taken from the earth is not apparently replenished. Modern thermal models of the earth, in fact, must take into account the radiogenic heat continually generated by the decay of the long-lived radioactive isotopes of uranium (U 238 , U 235 ), thorium (Th 232 ) and potassium (K 40 ), which are present in the Earth. Added to radiogenic heat, are other potential sources of heat such as the primordial energy of planetary accretion. Realistic theories on this were not available until the 1980s, when it was demonstrated that there is no equilibrium between the radiogenic heat generated in the Earth's interior and the heat dissipated into space from the Earth, and that our planet is slowly cooling down – albeit very slowly – less than 350C drop in the core temperature of about 4000C in 3 billion years!. The punch line is therefore that geothermal energy technologies are not truly renewable but instead harness energy which otherwise would be uselessly dissipated and the effect on the earth’s temperature is so infinitesimal that the technologies can realistically be regarded as renewable.

Milestones in the Development of Geothermal Energy

Geothermal resources range from shallow ground to hot water and rock several miles below Earth's surface, and even farther down to the extremely high temperatures of molten rock called magma. The uses to which the earth’s energy can be put depend on the temperature of the hot fluid extracted from it as illustrated below.

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Heat Pumps

The earth’s surface layer remains at an almost constant temperature between 10 to 16C (50 to 50F). Geothermal heat pumps use a system of buried pipes linked to a heat exchanger and ductwork into buildings. In winter the relatively warm earth transfers heat into the buildings and in summer the buildings transfer heat to the ground or uses some of it to heat water. Heating and air conditioning accomplished with one system!

Geothermal heat pump equipment in a Beijing apartment building

Source: NREL National Photographic Information Exchange

Direct Use

This relies on access to naturally occurring hot water which is most common in the earthquake zones such as the Pacific “Ring of Fire”. In the US most geothermal reservoirs are located in the western states, Alaska and Hawaii. The hot water can be used directly to heat buildings – residential, commercial and agricultural, and to assist in processes such as fish farming and vegetable dehydration.

Deep wells, a mile or more deep, can tap reservoirs of steam or very hot water that can be used to drive turbines which power electricity generators.

Schematic Geothermal Power Plant
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Historical Growth

Power generated from geothermal sources increased from increased by an average of about 3.5% per year between 1990 and 2000 (see figure below). In the decond half of the same decade, the energy produce from direct use of geothermal sources increased by over 13% per year!

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Associated Jobs

In 1996, the U.S. geothermal energy industry as a whole provided approximately 12,300 direct jobs in the United States, and an additional 27,700 indirect jobs in the United States. The electric generation part of the industry employed about 10,000 people to install and operate geothermal power plants in the United States and abroad, including power plant construction and related activities such as exploration and drilling; indirect employment was about 20,000.

What is more, geothermal, like other renewable energy industries, actually provides more jobs per MW of energy production than conventional (natural gas) power production as revealed in the table below

In the developing world, labor costs are much lower than in the USA, resulting in a correspondingly higher number of jobs per unit of energy production. If we assume the average jobs creation ratio in the developing world is twice that in the USA, it suggests that the geothermal power generation industry supported about 38,00 direct and 86,000 indirect jobs worldwide in 1996. By the year 2000, these figures had increased to approximately 48,000 direct and 128,000 indirect jobs respectively. These numbers of course neglect the significant contribution of jobs involved in heat pumps and direct use industries.

The Future

One of the most important economic aspects of geothermal energy is that it is generated with indigenous resources, reducing a nation’s dependence on imported energy, thereby reducing trade deficits. Reducing trade deficits keeps wealth at home and promotes healthier economies. Nearly half of the U.S. annual trade deficit would be erased if imported oil were displaced with domestic energy resources.

Nearly half of all developing countries have rich geothermal resources, which could prove to be an important source of power and revenue. Geothermal projects can reduce the economic pressure of fuel imports and can offer local infrastructure development and employment. For example, the Philippines has exploited local geothermal resources to reduce dependence on imported oil, with installed geothermal capacity and power generation to become second in the world after the United States. In the late 1970s, the Philippine government instituted a comprehensive energy plan, under which hydropower, geothermal energy, coal, and other indigenous resources were developed and substituted for fuel oil, reducing their petroleum dependence from 95% in the early 1970s to 50% by the mid-1980s. Developing countries will likely require increasing amounts of power in the coming years and there is a high probability they will use an increasing mix of renewables, including geothermal energy where possible. We have used the existing figures for Direct Use and Power Generation to calculate the combined geothermal energy production for 1995 and 2000. Countries have been grouped into either the developed (e.g. USA, Australia, UK) or developing world (e.g. China, Indonesia, Philippines). Possible growth into the future has been estimated conservatively using observed growth rates but setting anomalously fast growing countries to the average rate for the group. The results shown below show that total geothermal energy production could approach 100GW by 2010 with about one third in the developing world. Given the strategic attractions of renewables for the developing world, the relative comparison may be do a disservice to the developing world. Please note that the figures shown ignore completely any contribution made by geothermal heat pumps.

Within the USA, in California alone the CEC has estimated that planned geothermal developments could contribute over 4000 job-years in construction and over 2000 operating jobs by 2010. We have estimated the potential for job creation in the Developed and Developing worlds using the jobs/MW ratios observed in the USA; we have applied these asan average for the Developed world and doubled them for the Developing world. The resulting estimates shown in the figure below reveal the potential for the creation of about 1.3 million geothermal jobs by 2010.

Source: Greenjobs

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Education and TraIning:

Geothermal Education Office http://geothermal.marin.org/
Education-related Web site including worldwide geothermal resources map, an energy scrapbook, and classroom materials

UNIVERSITY OF CALIFORNIA, BERKELEY http://socrates.berkeley.edu/~rael/rael.html
The Renewable Alternate Energy Laboratory (RAEL) focuses on designing, testing, and disseminating renewable and appropriate energy
systems.

KANSAS UNIVERSITY http://www.mne.ksu.edu/~geocrack/
Modelling flow in fractured rocks. The primary application is geothermal reservoirs, where such capability is needed to simulate systems in which re-injection is used to circulate the fluid

OKLAHOMA STATE UNIVERSITY http://www.hvac.okstate.edu/
"Research of the Building and Environmental Thermal Systems Research Group includes building heat transfer, HVAC systems modeling, building energy simulation, hydronic heating systems, geothermal heat pump systems and ground loop heat exchanger technology."l OSU is also the home of the International Ground Source Heat Pump Association, whose goal is to "promote the growth and advancement of the geothermal industry while ensuring the quality, safety, and reliability of installed systems."

OREGON INSTITUTE OF TECHNOLOGY http://geoheat.oit.edu/
Development of geothermal energy resources. Although they are not a research funding source they do provide technical assistance in related technology development or applications. OIT also provides a clearinghouse service for geothermal development grants. Research at the Geo-Heat Center is supported in part by the US Department of Energy.

RICHARD STOCKTON COLLEGE OF NEW JERSEY http://phys.stockton.edu/geothermal_perspective.htm
Energy studies is an interdisciplinary program designed to educate students in problems associated with energy usage and to pose methods for possible solutions to those problems. "Energy prices and supplies are a major concern for homeowners, business people, and industry. The majority of residential and commercial buildings in the United States will have their energy efficiency drastically upgraded during the next decade. The geothermal heat pump project at Stockton is serving as a national model for such upgrades"

STANFORD UNIVERSITY http://ekofisk.stanford.edu/geotherm.html
Development of reservoir engineering techniques for efficient production of geothermal resources. The primary focus is to investigate reinjection into vapor dominated reservoirs such as The Geysers.

UNIVERSITY OF NEVADA, RENO http://www.unr.edu/geothermal/
Location and optimization of geothermal energy resources. The Center's team of scientists specializes in geochemistry, hydrogeology, geophysics, thermodynamics, remote sensing, seismology and structural geology (geologic mapping).

VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY http://geothermal.geol.vt.edu/
The Regional Geophysics Laboratory in the Department of Geological Sciences provides information on terrestrial heat flow and practical applications of low-temperature geothermal energy. The geothermal energy database includes temperature data from hundreds of temperature and other geophysical logs, rock thermal conductivity, and heat flow values from New Jersey to Georgia.

WASHINGTON STATE UNIVERSITY http://www.energy.wsu.edu/
Research, develops tools, and disseminates information to enable people to make informed decisions about energy. The program has been affiliated with the University since 1996. Previously it was part of the state energy office.

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