The word geothermal comes from the Greek words geo (earth) and therme (heat). So, geothermal energy is heat from within the earth. We can use the steam and hot water produced inside the earth to heat buildings or generate electricity. Geothermal energy is a renewable energy source because the water is replenished by rainfall and the heat is continuously produced inside the earth.
Geothermal energy is generated in the earth’s core, about 4,000 miles below the surface. Temperatures hotter than the sun’s surface are continuously produced inside the earth by the slow decay of radioactive particles, a process that happens in all rocks. The earth has a number of different layers:
The core itself has two layers: a solid iron core and an outer core made of very hot melted rock, called magma. The mantle which surrounds the core and is about 1,800 miles thick. It is made up of magma and rock. The crust is the outermost layer of the earth, the land that forms the continents and ocean floors. It can be three to five miles thick under the oceans and 15 to 35 miles thick on the continents. The earth’s crust is broken into pieces called plates. Magma comes close to the earth’s surface near the edges of these plates. This is where volcanoes occur. The lava that erupts from volcanoes is partly magma. Deep underground, the rocks and water absorb the heat from this magma. The temperature of the rocks and water get hotter and hotter as you go deeper underground.
Geothermal Energy uses:
People around the world use geothermal energy to heat their homes and to produce electricity by digging deep wells and pumping the heated underground water or steam to the surface. Or, we can make use of the stable temperatures near the surface of the earth to heat and cool buildings.
Some applications of geothermal energy use the earth’s temperatures near the surface, while others require drilling miles into the earth. The three main uses of geothermal energy are:
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 ground.
Geothermal Energy and the Environment
The environmental impact of geothermal energy depends on how it is being used. Direct use and heating applications have almost no negative impact on the environment.
Geothermal power plants do not burn fuel to generate electricity, so their emission levels are very low. They release less than 1 percent of the carbon dioxide emissions of a fossil fuel plant. Geothermal plants use scrubber systems to clean the air of hydrogen sulphide that is naturally found in the steam and hot water. Geothermal plants emit 97 percent less acid rain – causing sulphur compounds than are emitted by fossil fuel plants. After the steam and water from a geothermal reservoir have been used, they are injected back into the earth.
Geothermal features in national parks,are protected by law, to prevent the land from being disturbed.