Introduction :
Geothermal energy is a kind of energy stored in the outer shell of solid earth.
It’s clean,sustainable,endless and environmentally friendly.
This thermal energy is contained in the rock and fluids beneath Earth's crust. It can be found from shallow ground to several miles below the surface, and even farther down to the extremely hot molten rock called magma.
Geothermal energy is used in many applications ,such as ( to produce electricity,heat buildings,greenhouses,for industrial and other purposes ).
Earth contains in its interior ,a furnace containing a high temperature up to 4200 ° C .

Earth is composed of several layers and is from the inside out:
1. consists earth nucleus of two layers:
Interior is a core of solid iron and external
Therefore, if one digs 20,000 feet the temperature will be about 1900C above the surface temperature. This difference will be enough to produce electricity. However, no useful and economical technology has been developed to extracted this large source of energy.
• Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to Normal Geothermal Gradient, but the gradient is 400C/km dug underground.
• Molten Magma: No technology exists to tap into the heat reserves stored in magma. The best sources for this in the US are in Alaska and Hawaii.

USES OF GEOTHERMAL ENERGY:

1) Direct Use and District Heating Systems which use hot water from springs or reservoirs near the surface.

2) Electricity generation in a power plant requires water or steam at very high temperature (300 to 700 degrees Fahrenheit).
Geothermal power plants are generally built where geothermal reservoirs are located within a mile or two of the surface.

3) Geothermal heat pumps use stable ground or water temperatures near the earth's surface to control building temperatures above