How to Use the Cores Heat With Geothermal Energy
Have you ever seen a geyser or hot spring eject millions of gallons of boiling water and hot steam upwards into the earth's atmosphere. There's an enormous amount of energy beneath our feet, in the core of the earth, and tapping into this free energy source is known as Geothermal Energy. The actual word geothermal comes from the combination of the Greek words, geo (meaning earth) and therme (meaning heat). So the literal translation is 'heat from the Earth'. So the expression geothermal energy literally means energy from the heat of the Earth.
Because this is a naturally occurring phenomenon, Geothermal Energy is a truly renewable energy resource. As you probably know, our planet has a molten core. Some 4000 miles below us, a boiling mass of molten rock is continuously swirling around and this resulting liquid rock moves upwards though fissures and cracks towards the surface. At the core of the Earth, temperatures reach an incredible 9000 degrees Fahrenheit, and the origin of this heat was created around four billion years ago during the creation of our planet.
It's believed in many scientific circles that the inner core is continually undergoing radioactive decay, meaning that the heat just keeps on regenerating. As the liquid rock moves outwards, it comes in contact with the cooler rock surrounding it. Under the immense pressure and temperature this exerts, the cooler mantle type rock melts, becoming less dense as it rises towards the surface. This liquid rock is known as magma, which we see at the surface erupting from volcanoes.
However, most of this magma remains well below the surface, which heats the rock around it, and any water. If there are cracks or openings, this water, sometimes heated to as much as 700 degrees Fahrenheit exits at the surface as geysers, hot springs or bubbling mud pools. But most remains trapped beneath the surface, forming natural 'geothermal reservoirs', and it's these reservoirs, which are tapped into to create geothermal energy.
So How Does Geothermal Energy Work?
Because these underground reservoirs of heated water stay at a pretty much constant temperature, we can tap into this to provide both a direct and an indirect energy source. Using a series of pipe that are inserted beneath the ground, this heat energy within the water can be drawn up to the Earths surface and then used in a number of different ways for heating, power generation or direct use of this hot water itself.
Although in essence we are extracting a natural source from below the earth, this is in no way to be thought of as 'mining'. The difference between mining and extraction of geothermal energy is that the Earth is constantly renewing these heated, trapped water reservoirs. In mining, however, minerals and content are removed from the Earth forever sometimes never to be replenished.
Geothermal energy emits virtually no greenhouse type gases, it is cheap and requires no additional fuels to power it. In terms of being friendly to the planet, this is one the most advantageous energy sources that's available to us and its all free below our feet.
There are basically three different types of 'Geothermal Energy' uses available to us.
- Geothermal Power Plants - This is were vertical holes called bore holes are dug directly into the heated underground reservoirs. The heated water and steam, naturally heated to super-hot levels are harnessed and used to drive turbines for the generation of electricity.
- Ground Source Geothermal Energy - When the geothermal reservoirs are not too far below the surface, a series of long heat absorbing pipes or shallow bore holes may be used to easily access the naturally occurring heat and energy. The thermally conducting liquid circulating around the pipes absorbs the heat which is extracted using ground source heat pumps.
- Direct Geothermal Energy - When the geothermal heated water is very near to the Earth's surface, it could be directly extracted for many uses such as washing, bathing such as volcanic spas or for the heating of buildings.
In volcanically active countries, like Iceland, geothermal power plants take full advantage of this free natural energy source. By pumping the super-heated water upwards, when it reaches atmospheric pressure it turns into steam which is used to power generators and turbines to create electricity. Where it is practical to do so, geothermal power plants can provide more than a third of a country's energy needs.
Geothermal energy is also becoming a very popular source of domestic heating and air-conditioning, thanks to the low cost compared to using oil or gas. This is done by using what is called a 'geothermal heat pump' or 'ground source heat pump'.
A series of pipes filled with a mixture of water and a thermally conductive liquid is buried beneath the ground, at a depth of up to 12 feet. Operating on a basis similar to that of a refrigerator, just in reverse, it can move heat in both directions. In the winter months the heat is drawn into the home, providing the central heating, and in the summer it's drawn out and returned to the Earth, providing air conditioning.
One of the main disadvantages of using geothermal energy as a renewable energy source in any of the above scenarios are that of ground and waste water pollution. It also is a relatively expensive system to install and maintain and naturally will have some geographical restrictions. Although it might seem advantageous to place a geothermal power plant close to a volcanic source, in reality, the nearer it's located, the more likely there are to be operational risks and issues.
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By Peter Emson