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How does Geothermal Drilling Work?

By Ken Black
Updated: May 21, 2024

Geothermal drilling is a process whereby heat is taken from the Earth and used in a productive way for energy needs. The heat can be used directly for some needs such as space heating, but the true value for the mass market comes from that heat's ability to be converted to other forms. Electrical generation is one of the most common reasons for geothermal drilling on an industrial scale.

Geothermal power is one of the great untapped resources in many locations around the Earth. Physics teaches that much of the universe's energy is in the form of heat and that humans have typically failed to make good use of the heat they have. Even in energy conversion of other forms, the reason for the loss of efficiency is heat generated from the conversion that is never used for any practical purpose.

Geothermal drilling seeks to change this. By drilling holes deep into the Earth's crust, especially in certain regions of the world, such as the Pacific Rim, there is the possibility of accessing vast stores of energy. Geothermal well drilling can be a major process as these wells may go down three miles (5 km) or more, depending on where in the world they are located. While there is heat available in all parts of the world, some places would have to dig much deeper than this, making getting geothermal energy difficult. Thus, the costs for geothermal drilling in those areas would likely exceed the benefits.

Once the well has been drilled, there is a virtually endless supply of energy. Further benefiting geothermal drilling operations is the fact heat rises, meaning there is very little in the way of mechanization needed to bring the energy to the surface, once the route has been created. However, the process does not simply end with the geothermal drilling. It must still be converted into useful energy.

In some cases, the energy conversion is not needed. This is most commonly seen when the energy is used for space heating. However, this is an entirely different situation altogether from commercial geothermal drilling. In this case, the geothermal well does not need to go nearly as deep. Just a few feet below the ground, the Earth stays nearly a constant temperature of between 50 and 60 degrees Fahrenheit (10 to 15.5 degrees Celsius) in nearly all locations. Therefore, the air only needs to be heated approximately 10 more degrees to make it comfortable.

If conversion is needed, this is usually accomplished by producing steam. Some wells already do this naturally, further simplifying the process. In other cases, steam is created using the heat available. That steam then rotates turbines, which produce the electricity. Once drilled, geothermal wells offer a very clean source of energy void of pollutants or greenhouse gasses. As a usage note, geothermal may sometimes be written as two words: geo thermal.

All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By anon251994 — On Mar 03, 2012

Interested parties should follow Geodynamics progress in drilling Habanero 4, due to start March 2012 to tap bottom hole temperatures of 240 degrees C.

By PelesTears — On Mar 13, 2011

@Aplenty- in my opinion, the next big advancement in geothermal energy will be the use of geothermal heating and cooling. This can be accomplished almost anywhere, and can provide heating and cooling with little cost and maintenance for both residential and commercial properties. By integrating energy systems into the built environment, whether they be passive or active, will be one of the most important ways to reduce energy consumption in the near term.

By aplenty — On Mar 12, 2011

@Anon77298- Good point! I read a story about a geothermal drilling rig in Basel, Switzerland that caused a moderate earthquake, suspending the entire project. Many geothermal projects are located in seismically active zones, and drilling through faults can have consequences like the accident in Switzerland. Most of the earth's easily accessible geothermal resources have already been exploited so the remaining resources are only becoming more and more dangerous to access.

This shows that no technology will be perfect, and there will always be some type of obstacle that will need to be overcome. I do think that geothermal is a better option than things like coal, oil, and gas electricity generation since they produce larger waste streams and send a number of toxic pollutants into the atmosphere.

By anon77298 — On Apr 13, 2010

Geothermal drilling is not always "void of pollutants". Many geothermal areas produce large amounts of salt, minerals and gases along with the hot water. This creates a disposal situation.

The salts and minerals can clog up turbines and pipes, creating expensive cleanup operations and corrosion that shorten the life and add cost to the energy production.

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