Monday, February 17, 2014

Quick guide to geothermal energy extraction

Geothermal energy is abundant renewable energy resource that is yet to fulfill its immense potential because geothermal energy is currently being harnessed in only 24 countries of the world, with U.S. still being the world’s largest geothermal producer. Harnessing geothermal energy refers to extracting heat below the Earth's surface for electricity generation and for heating/cooling purposes.

Geothermal energy is basically a heat within the Earth's core. This heat remains at a relatively constant temperature throughout the entire year, meaning that geothermal energy does not suffer from intermittency issue like this is the case with solar and wind energy, and is available 24-7 without the need for some backup energy storage solution. This naturally available energy is extracted by a series of pipes filled with water buried below the Earths surface. This hot water is then used in our homes for heating purposes or to generate electricity.

Geothermal Power Plant - Hot water is pumped from deep underground, turned to steam to power turbines and generate electricity, cooled back to water and then pumped back into the Earth.
What is the main working principle of geothermal energy? Within the Earth's core, somewhere around 4000 miles below the surface, temperatures can reach over 9000 degrees Fahrenheit. This enormous amount of heat originated four billion years ago in a fiery combustion of dust and gas in time when our planet was created. It is the radioactive decay of the inner core that keeps the heat generating and flowing outward from this inner core to the mantle of harder rock which surrounds the core. Once the temperature and pressure reach high enough levels, some of this mantle rock melts. Then, because the melted rock or magma has lesser density when compared to surrounding rock, it rises and moves slowly up to the Earth's crust.

In rare occasions the hot magma moves all the way to the Earth's surface in a form of a volcanic eruption, but in most cases the magma remains underground and heats the adjoining rock as well as any water that has seeped down through holes and cracks. Some of this water, whose temperatures can reach as high as 700 degrees, travels back up through cracks to the Earth's surface and emerges in forms of hot springs and geysers. In most cases, however, the water and magma are trapped within the rock, forming a natural underground geothermal reservoir. It is these underground geothermal reservoirs that are the enabling us the extraction of geothermal energy for the purposes of heating and generating electricity.

Geothermal Heat Pump - In winter cold air or water is pumped trough underground pipes to heat, and in the summer hot air or water is pumped trough underground pipes to cool. 
In order to use geothermal energy for heating/cooling purposes one needs to install geothermal heat pumps. Geothermal heat pumps are significantly more efficient compared to conventional heating and cooling systems and their main advantage is the fact that they can move heat in two ways: during the hotter summer months, the geothermal heat pump operates by removing the heat from the building and dissipating it back into the ground, while in the cold winter months heat gets withdrawn from the ground (the heat source) and is used to heat building.

The process of using geothermal energy for electricity generation is as follows: extremely hot water from the underground is pumped to surface and once it reaches surface it turns to steam where it is used to power turbines that generate electricity.

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