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Energy

"Geothermal energy is begging to be used"

Ernst Huenges, who leads the German Research Centre for Geosciences (GFZ), says there's huge potential to extract energy from the heat and water resources within the earth in order to meet the world's energy needs.

An expansive power plant, complete with smokestacks that emit pollutants (Foto: GZB)

In geothermal plants, the earth's warmth is used to produce heat energy as well as electricity

GLOBAL IDEAS: Why is geothermal energy an important option for the future of our energy supply?

Ernst Huenges: Geothermal power is a source of energy that is still begging to be used. It’s interesting to note that residual heat generated during the earth’s creation is still stored deep in its core, but around two thirds of the geothermal energy produced today is tapped from the earth’s crust. (Editor’s note: through natural radioactivity) Geothermal energy draws ist source from about 30 to 60 kilometers deep under the earth. But even with the technology available today, we’re still limited to the first ten kilometers. Essentially, geothermal energy is widely available everywhere. Because the earth’s heat cannot be transported, the sensible thing to do is to search for sources of that energy everywhere. The amount of effort needed to extract it differs from one place to the next. There are regions, like Central America for example, where it is easy to tap into geothermal energy. There are already good projects in Central America that work on transforming the earth’s heat into electricity. And of course, any country with active volcanic regions, such as Indonesia, are perfect candidates.

In many countries, geothermal power is one of the primary sources of energy. China is the world’s geothermal leader followed by Sweden and the US. Iceland is in fourth place. In the Icelandic capital Reykjavik, 90 percent of the city’s homes get their energy supply from a geothermal field.

You mentioned electricity. So does that mean it is possible to produce electricity using geothermal energy?  

Professor Ernst Huenges

Professor Ernst Huenges heads the Geothermal Deployment team at the GFZ in Potsdam near Berlin

There are various ways to turn heat into other forms of energy. It can be transformed into steam power, for example, which can be used to generate electricity. And heat can even be turned into cold energy, like in absorption cooling systems. That could be a very interesting option in the future, especially in the world’s hottest areas. In those regions, people don’t need heat: they consume a massive amount of cooling energy. And that can actually come from the earth’s warmth. 

So essentially, there is no limit to the earth’s supply of heat....

The potential is huge. The latest IPCC (Intergovernmental Panel on Climate Change) report says that geothermal potential is so great, it almost can’t be measured. And if that’s the case, then geothermal energy really should be one of our number one options in the future when we think about sustainable energy. It can involve a lot of effort on a regional level, though, and sometimes poor engineering produces more problems than benefits. There have been cases where the goal was simply to make money as fast as possible, and the earth wasn’t given the chance to restore its heat. A lot of expertise and know-how is needed to access and make use of geothermal energy. Researchers here at the GFZ help train people in countries all over the world, like Indonesia, so that we have enough engineers who are capable of unearthing the natural treasure.

A geyser in Iceland shoots a stream of hot water into the air
(Foto: CC/ToNG!?)

Important sources of energy are right underneath the earth we walk on


How does geothermal energy help contribute to curbing climate change?  

The IPCC report also shows how sustainable geothermal energy is. When it comes to CO2 emissions - which are created in any technological process - geothermal energy only releases a small fraction of the emissions that are involved in the use of fossil fuels. So if we replaced our fossil fuel sources with geothermal ones, we could slash the level of our CO2 emissions by anywhere from two to five percent. So geothermal power really is a energy option that needs to be taken seriously.

According to an IPCC special report called "Renewable Energy Sources and Climate Change Mitigation," using renewable sources of energy - including geothermal - could slash global CO2 emissions levels by a third by the year 2050. Currently, it’s estimated that more than 30 giga tons of CO2 are emitted every year worldwide. One optimistic prognosis predicts renewable sources could make up 43 percent of the global energy mix by 2030, and jump to as much as 77 percent by 2050.

What are the risks involved in the use of geothermal energy?

Three workers operate a deep drill(Foto: K. Winkler/GZB)

Extracting the earth’s heat is a complicated process

Besides the economic risks, there are also issues that have emerged in actually accessing the energy. Drilling technology is well-developed - we have had it for more than 100 years. There are engineering and technical regulations that must be followed during drilling projects. Yet there are examples where the simplest rules were not heeded and that led to problems that actually have nothing to do with geothermal energy. They have to do with negligence. The risk of causing tremors or seismic activity is very low, but that’s why it’s important to have specialized know-how and extreme precision and diligence. And it is important to know that materials and substances such as naturally radioactive elements exist underground that can be released when water is circulated. So it’s crucial to make sure the water circuit stays closed. So far, there have not been any incidents or significant damage linked to geothermal energy, and nobody has been injured.

In the southern German town of Staufen in Breisgau, workers who were drilling to provide geothermal heat for the town hall ran into some serious complications. It is believed that they drilled too deep, hitting a groundwater conductor and causing the water to rush into a sequence of rock strata that contains the chemical compound anhydride. The resulting reaction produced gypsum, a sulfate mineral that expands. The consequences were disastrous: cracks started to appear everywhere and the ground started to rise, severely damaging more than 200 homes and destroying the town.

But when you hear about all the things that have to be considered in harnessing the energy and the kind of effort that goes into it, can a geothermal facility really be operated in an economically sustainable way in the long-term?

Yes, of course. In some developing countries, geothermal energy has a significant share in the energy mix. There are several countries such as El Salvador in Central America where geothermal energy accounts for around 20 percent of energy supplies. East Africa has also started to develop geothermal technology, and that only happens if it actually pays off. If you look at the high costs involved in working with fossil fuel energy sources, it is clear that geothermal energy can be economically viable without any major price pressure.

But the start-up costs are fairly high. Is geothermal really an option for developing countries, too?

A close-up image of a drill (Foto: GFZ Potsdam)

It takes massive drills to reach deep into the earth and tap geothermal potential

Yes. East Africa for example has great potential but it is unfortunately quite poor and doesn’t necessarily have the engineering infrastructure needed. But I know Kenya is working hard to educate people in geothermal engineering. Precisely because of the high start-up costs, it is important for industrial countries to lend a helping hand by investing in projects. And they do, through the World Bank. What’s more, we have plenty of examples of geothermal projects that have lasted for long periods and that is a sign that it’s not a quick operation that falls apart if investors pull out.  

Do you see that as a chance for developing countries to gain contacts and access to industrialized nations?

For those developing countries that have geothermal potential, yes, definitely.

So would you say geothermal power is a energy form for the future?

Geothermal power will act as a stabilizing force in the future because it can be used around the clock and in every season. There is the potential to meet all our energy demands with just geothermal sources, but the effort behind that is too great. Instead, you can combine a series of clean energy sources including sun, wind, and – as long as there are no issues of conflict – hydropower and biomass. But geothermal will certainly be a significant part of the energy mix.

Author: Po Keung Cheung / ss
Editor: Sonia Phalnikar

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