I. Overview of Geothermal Energy Geothermal energy (from the Greek words geo [earth] and therme [heat], thus 'earth heat' energy) is a domestic energy resource with cost, reliability, and environmental advantages over conventional energy sources. Energy from this source comes from the renewable source of heat from deep in the Earth (diagram: A). Heat is brought up to near the surface by thermal conduction (diagram: B) and magma. This heat heats ground water to form hydrothermal resources (naturally occurring hot water / steam in fissures [diagram: C / D]). Wells (diagram: F) are drilled to tap fissures for hot water, and the steam can be used to generate electricity, as described in the next section.

Hot water may also emerge on the surface as hot springs or geysers (diagram: E). Utilizing geothermal energy not only contributes to our energy supply, but also reduces energy demand (through the use of geothermal pumps to heat and cool buildings, reducing the need for natural gas and other nonrenewable resources). It is unfortunate that only a small part of our geothermal resources are being used today. Hot water, at temperatures between 300 and 700 degrees Fahrenheit, is brought from an underground reservoir to the surface and is converted to steam by using changes in pressure. The steam and liquid are separated, with the steam turning turbines (generating electricity) and the water is injected back into the reservoir to maintain the chamber's pressure. Sometimes the hot water is used directly for home, and sometimes greenhouse, heating.

It is also used to speed up the growth of aquatic animals (aquaculture). II. Dependency on Geothermal Energy Although we (the United States) are not taking advantage of all of the geothermal sources in the United States, the source is here today; it is not merely a hope for the future. The production of geothermal energy ranks third in the country' renewable resources, behind hydroelectric power and biomass conversion. Worldwide, there are more than 7,000 megawatts of electricity being generated. This is equivalent to production of about seven nuclear power plants..

Benefits: Energy Efficiency As a result of today's use of geothermal energy, the consumption of nonrenewable resources is slowed down, resulting in subsequent slowing down of acid precipitation and the release of greenhouse gases caused by fossil fuel use. Sources of this type of energy are found in many places on the Earth. Its use has helped developing countries such as the Philippines, Indonesia, and nations in South America and Eastern Europe. Italy, the US, and other developed nations are also using geothermal energy. Contrary to popular belief, there is a large geothermal base in the US, and generally speaking, in the world.

In fact, according to the US Department of Energy, "the resource base for renewable energies- geothermal, solar, biomass, and wind- is much larger than the total resource base in coal, oil, gas, and uranium". No current technology is more efficient in home heating and cooling than the geothermal heat pump. The pump operates on the same principle as the refrigerator, but it can move heat in both directions. In the winter, heat is removed form the ground; in the summer, hear is removed from the house. In either cycle, water is heated and stored, providing hot water.

Because electricity is used only to transfer heat (not to produce it), these heaters will deliver around four times more energy than it consumes. IV. Benefits: Environment Currently, electrical utilities account for three-quarters of sulfur-dioxide emissions (acid rain), a third of nitrogen-oxide emissions (inducing formation of ground-level ozone, smog), a fifth of the gases linked to the greenhouse effect, and half of all nuclear waste. Geothermal power plants produce much less, if none, of those listed. Geothermal plants also take up very little land space.

Things cans be built nearby without fear of disaster. V. Benefits: Economy Approximately a quarter of our trade deficit is attributed to oil imports, which now amount to half of the oil we use here in the US. We are becoming more and more dependant on foreign energy supplies. If we cut oil imports, and increased geothermal energy use, our energy security would rise, while our trade deficit would decrease. VI. Limitations There are three main limitations on the use of geothermal energy. The first is that, although there is geothermal energy all over the earth, a place may be too far away from an area where energy could be produced to effectively take advantage of the resource (i. e., you would need to dig very deep into the Earth to harbor heat needed for geothermal energy to be utilized; this is not cost effective).

The second is that, although geothermal energy will quickly pay for itself, it is relatively expensive to start a geothermal plant, which would include testing land, building, tunneling, etc. The last problem is that the heat's earth-passageways corrode and need maintenance and up-keeping work, which may lower the appeal and efficiency of this energy source.