Geology And Geophysics

Geothermics an Introduction



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Our ancestor's probably guessed that the center of the Earth was hot by witnessing volcanic eruptions, steam vents, geysers, and hot springs. It was not until people began excavating mines deep into the earth that they were able to take temperature measurements and determine that, yes, the deeper we go, the hotter it gets.

The heat generated deep in the earth is called geothermic energy. Some rocks in the earth's crust are as hot as 1,800 F (1,000 C) making the earth a storehouse of heat energy. Some of this energy makes its way to the surface in the form of hot water springs, geysers or fumaroles (steam vents). An alternative means of extracting this heat energy is to pump water down into the earth and bring back hot water and steam. This water can then be used for heating or generating electricity. The first countries to use geothermal energy were Japan, The Geysers in California, USA, New Zealand and Mexico. More than 20 followed in the years to come.

The earth continually generates radiogenic heat by the decay of the radioactive isotopes of uranium, thorium, and potassium. Harnessing the energy from geothermal sources uses energy that would naturally be dispelled into the atmosphere, though this energy source is not technically renewable. The heat generated in the Earth's interior slowly dissipates into space. Our planet is slowly cooling down. The change in temperature however, is so infinitesimal that the energy source is typically regarded as renewable.

Geothermic energy technologies tap the heat generated deep in the earth's interior as an emission-free source of power. Reykjavik, Iceland was once a city plagued by dirty air as a result of fossil fuel emissions. (www.geothermal.marin.org) Currently, nearly every building in Reykjavik is heated using geothermal power. Since introducing geothermal power, Reykjavik has become one of the cleanest cities on the planet.

In many developing countries, geothermal energy is available locally and is sometimes the only form of energy available. Use of geothermal energy makes good economic sense. One of the benefits of geothermic energy is that it is an indigenous resource. Its use reduces a countries dependence on foreign energy sources, reducing trade deficits and spurring development of the local infrastructure and employment opportunities.

Using Geothermic Energy

Currently, our ability to make use of this energy relies on specific geological conditions. An accessible carrier (water or steam) is required to transfer the heat from deep in the Earth to the surface. Sources of geothermal energy range from shallow ground to hot water and rock several miles below Earth's surface. Its main application is in using natural concentrations of hot water for use in electric power generation and direct heat applications such as space heating, agriculture, and spas. In Russia alone, there are over 4,000 spas that use water heated by geothermal energy.

Heat Pumps
The Earth's surface layer has a constant temperature of about 50 - 60F (10 16C). Geothermal heat pumps use a system of buried pipes to pump water deep into the earth where it is heated before returning to the surface. In winter, the water is warm relative to the cold surface temperatures. Heat transfers into the buildings. In the summer, systems transfer heat into the ground or use it to heat water.

Direct Use
Geothermal reservoirs of hot water are commonly located in earthquake zones such as the Pacific Rim. In the US, geothermal reservoirs are located in nearly all the western states, Alaska, and Hawaii. The hot water can be used directly to heat buildings or in processes such as fish farming, agriculture and industrial uses.

Electrical Production
Geothermic energy provides alternative sources of steam required by power plants that typically burn fossil fuels or utilize nuclear energy. Geothermal systems drill to depths of up to 10,000 ft (3000 m) to access the hot water and steam heated by the deep magma. The steam is purified before being transported in large, insulated pipes and then used to power turbines that produce electricity.

Growth
Power generated from geothermal sources According to the International Geothermal Association, the amount of energy produced by geothermal sources has increased an average of 3.5% per year from 1990 to 2000.

The amount of geothermic energy available from the Earth is enormous. As technological advancements allow more efficient use of this important resource, the opportunities to develop new applications and the concomitant employment opportunities will grow as well.

For more information:
http://iga.igg.cnr.it/geo/geoenergy.php

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