Geothermal Energy Definition & History

Archaeological evidence establishes that the beginning of man’s application of geothermal energy in North America came about more than ten thousand years ago with the settlements of Paleo-Indians at natural thermal springs. The natural springs functioned as a reservoir of heat and purifying, their minerals as a source of therapeutic healing.

Although people still soak in shallow pools heated from the Earths core, technologists are creating technologies that will permit us to examine areas more than ten miles beneath the Earth’s surface hunting for geothermal resources.

Geothermal Energy is heat (thermal) retrieved from the sub terrain depths of the land. The thermal energy held in in the rock of the earth and liquid (that occupies the cracks and pores inside the rock) in the earth’s crust.

Scientific calculations determine that the earth, starting from an entirely molten state, must have cooled off and become entirely solid several thousand years ago without an energy stimulant in addition to that of the sun. It is thought that the elemental source of geothermal energy is radioactive decay occurring deep within the earth (Burkland, 1973).

In most areas, this heat reaches the surface in a very diffuse state. However, due to a variety of geological processes, some areas, including substantial portions of many western states, are underlain by relatively shallow geothermal resources.

Humans have utilized geothermal resources in North America for more than 10,000 years. Paleo-American Indians used thermal springs for cooking, and for sanctuary and relief. Hot springs were neutral areas where members of fighting nations would bathe collectively in serenity. Native Americans have a history with every major thermal spring in the USA.

These geothermal springs can be separated as low temperature (less than 90°C or 194°F), moderate temperature (90°C - 150°C or 194 - 302°F), and high temperature (greater than 150°C or 302°F). The roles which these resources are given are also regulated by temperature. The highest temperature sources are mostly utilized solely for electrical power generation. Current U.S. geothermal electrical power generation totals roughly 2200 MW or close to the equivalent of 4 large atomic power plants. Uses for low and moderate temperature sources can be separated into two classes: direct use and ground-source heat pumps.

Direct use, as the name implies, requires applying the heat energy in the water directly (without a heat pump or power plant) for applications such as heating of buildings, industrial works, greenhouses, aquaculture (farming of fish) and holiday resorts. Direct use projects more often than not use resource temperatures between 38°C (100°F) to 149°C (300°F). Current U.S. Established capacity of direct use schemes totals 470 MW or sufficient enough to heat 40,000 average-sized homes.

Ground-source heat pumps utilize the terra firma or groundwater as a heat source in wintertime and a heat sink in summertime. Utilizing resource temperatures of 4°C (40°F) to 38°C (100°F), the heat pump, a mechanical device which moves heat energy from one area to another, transposes heat energy from the soil to the home in winter and from the house to the soil in summer. Precise information isn’t available on the current number of these arrangements; yet, the rate of installation is believed to be between 10,000 and 40,000 per year.

The current production of geothermal resources from all uses currently sits third amongst renewable energies, behind hydroelectricity and biomass, and in front of solar and wind. Despite these impressive statistics, the current level of geothermal use pales in comparison to its potential. The key to wider geothermal use is greater public awareness and technical support–two areas in which the Geo-Heat Center of America is very active.