Where Does Geothermal Energy Come From

Earth's core.
Earth's core.


You may not have heard much about geothermal energy but it is one of the hottest alternative energy commodities around. It is a renewable and clean energy source that will be around for a long time. However where does geothermal energy come from? The answer is the earth itself. The world geothermal comes from the Greek words geo which means earth and therme which means heat. Basically geothermal energy is heat energy harvested from the Earth itself.

Geothermal heat is produced by the core of the Earth itself. You may not think that energy to be much when compared to the sun but you would be wrong in some aspects. The Earth’s core alone is 11,000 degrees. That is hotter than the surface of the sun. The Earth’s geothermal energy is created by the decay of radioactie materials in the core and in the surrounding layers of rock.

However this still doesnt tell us how this energy becomes accessible. The deepest mankind can even go with the best technology is around 11 km. The answer is plate tectonics. bounadaries and faults are cracks in the Earth’s crust where magma rises near or to the surface. Geothermal plants take advantage of this fact using water heated by this volcanic activity to produce electric power.

The main place where geothermal energy can be used have not only volcanic activity but also enough ground water to be used to power the turbines that generate power. Prime areas are near volcanoes, hot springs, and geysers. Large volcanic islands like Greenland have vast resources in terms of geothermal energy. In the end the most common location for geothermal reservoirs will be where ever there are major plate boundaries with a lot of seismic and volcanic activity.

The benefits of geothermal energy is already being discussed in nations like Iceland as way to reduce reliance on foreign oil. Geothermal is abundant where it can be accessed and can easily produce energy on par with the output of other types of energy production such as nuclear reactors. The best part is that it is clean energy. There is no way it can produce pollution that can harm the environment. The only risk is that drilling in active volcanic area can make them vulnerable to earthquakes.

In the end Geothermal still one of the best possible sources of clean energy on the planet. As the technology improves for accessing it more homes around the world will have the opportunity to be powered by this renewable energy resource.

We have written many articles about geothermal energy for Universe Today. Here’s an article about Geothermal Energy, and here’s an article about how geothermal energy works.

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.


How Does Geothermal Energy Work

Geothermal Hotspots
Geothermal Hotspots

In order to understand why geothermal energy is considered an environment friendly alternative to fossil fuel, you must first be familiar with the basic workings of this technology. So how does geothermal energy work?

First of all, geothermal energy can be used in a variety of ways. There are those who utilize the heat directly for home heating (and even cooling) systems. Others use them in greenhouses, fish farms, and spas. Of course, I haven’t forgotten its most celebrated application – to produce electricity.

Thus, in answering the question, “How does geothermal energy work?”, one must first specify the specific application of the energy.

For those applications which utilize geothermal energy directly like those in fish farms, spas, and greenhouses, hot spring water is simply tapped from underneath the ground surface and redirected into these facilities.

The hot water may get its heat from magma that is able to creep upward and heat its surroundings, including the groundwater there. Magma doesn’t have to contribute heat directly though, as this melted mantle material can be found very deep underground and hence difficult to gain access to.

In some cases, where magma isn’t found in the direct vicinity, you can still obtain hot water by simply drilling deep in the ground. Always remember that the deeper you drill, the hotter the temperature gets.

Geothermal energy used to power household room heaters are extracted from the ground (not through water). During winter, ground underneath the surface is warmer than the temperature above. Heat is then extracted by using geothermal heat pumps. A typical geothermal heat pump extracts heat through a series of pipes containing either circulating water or an antifreeze solution, just like a refrigerator or an air conditioning unit.

Now for the last application mentioned earlier. How does geothermal energy work in the case of geothermal power plants?

Just like most power plants (e.g. hydro and wind power), energy is converted to electricity through the use of turbines. There are three ways of doing this.

One method directs hot steam drawn from underground into the turbine. Another draws extremely hot water from underneath, flashes it into steam, which is then directed to the turbine. The third method makes use of a heat exchanger to transfer heat from hot water drawn from underground unto a fluid (isobutane is commonly used) that is directed to the turbine.

In all three methods, the turbine is responsible for converting the kinetic energy of the directed fluid (which makes it turn) into electricity.

Universe Today has some interesting topics related to geothermal energy which you might be interested in. Here are two of them:
Geothermal Heat
Geothermal Heating

You can find more information about geothermal heat pumps from the US Department of Energy as well on the Energy Star website.

Tired eyes? Perhaps you’d like to listen to some Astronomy Cast episodes instead:
Volcanoes, Hot and Cold
Space Elevators