Geothermal Energy

During winter, my mind wanders around a lot. Mostly it travels southwards, but occasionally the journey is in 3-D, from the farthest galaxies¹ to the center of the earth.

Though mother earth is pretty cool on the surface, she's despite her age still a hot girl, and when I look out of the window (snow, snow, and more snow) I like to remind myself that we're all just sitting on a thin layer of cold stones below which our planet is dynamical and full of energy.

In 1864, Jules Verne wrote his fantastic novel 'Journey to the Center of the Earth' , and today I read there will be a new remake of the movie, called 'Journey 3-D', which is advertised with "Journey 3-D will be shot in live action, with the otherworldly landscapes and creatures supplied by high-definition, photo-real 3-D technology.".

But there's a very realistic side to the fantastic travels. Since the beginning of the last century, geothermal power plants have been build to use the energy of the earth's heat. The first geothermal power plant was built 1904-1911 in Larderello, Italy - in an area once known as Valle del Diavolo (Devil's Valley) for the boiling liquid that bubbled out of the ground. The power plants in Larderello were destroyed during World War II, but have since been rebuilt and expanded.

One can roughly distinguish four conceptually different technologies for geothermal power plants. In case there is a natural reservoir, one can either

1) Use the hot water from the geothermal source to route it directly through a turbine to produce electricity. When the hot water is released from the pressure of the deep reservoir, part of it flashes (explosively boils) to steam. Therefore these power plants are also called 'Flashed Steam Plants'. The force of the steam is used to spin the turbine generator. To conserve the water and maintain reservoir pressure, the geothermal water and condensed steam are directed down back into the periphery of the reservoir. You can look at a virtual tour provided by calenergy.com: for Quicktime or Windows MediaPlayer.

2) Or, in case the geothermal reservoirs produce mostly steam and very little water, the steam goes directly into the turbine. The largest known field in the world is the Geysers dry steam reservoir in northern California, which has produced electricity since 1960, and, after 40 years, still produces enough electricity to supply a city the size of San Francisco.

These conventional geothermal power stations are generally limited in size and unfortunately are often linked to emissions of volcanic gases and toxic elements. A more sophisticated version to extract the energy is to

3) Pass the hot water from the geothermal source through a heat exchanger, where it is transferred into a second cycle. These type of power plants are therefore called 'Binary Cycle'.

Besides these technologies relying on naturally occurring water resources, there is the more recently developed

4) 'Dry Hot Rock' technology, which makes the energy extraction independent from the natural water or steam resources. All one needs is, well, a dry hot rock that shouldn't be too far below the surface. The current limit for efficient mining is approx 5 km (3 miles) underground. Water is pushed into the hot rock, where it gets heated and due to its own pressure then rises through drill holes back to the surface where energy can be extracted. For more information, see e.g. this website.


The Deep Heat Mining project in Basel, Switzerland, is based on this technology. It was stopped last month following a series of small earthquakes whose center was located at the construction site.




Of course the use of geothermal energy crucially depends on the local conditions. Iceland has a vast reservoir of easily accessible sources, and I would have guessed Iceland is leading in that area. But to my huge, and pleasant, surprise I read at the website of BP

'The US leads the world in installed geothermal power capacity.'

Checking the references, I found the source in this statistic about Worldwide Geothermal Power Generation, Table 1, from the GRC which confirms the leading role of the USA. And it is a lively area of research: Only last week I read about the results of a MIT study:

SciAm, January 22, 2007, U.S. urged to ramp up geothermal power

'MIT's study [...] said the United States as a first step could achieve capacity of 100,000 megawatts - enough to supply about 25 million homes -- in 50 years at an eventual cost of just $40 million a year. That would represent about 6 percent of the current U.S. electricity supply.'

(see also Physorg.com: MIT releases major report on geothermal energy).

Though geothermal energies will not be able to cover the world's increasing need for energy, it is an alternative source whose potential has not yet been fully explored, and I am happy to see that efforts go into this direction. The world's energy supply is a problem that we have to face, or our journeys in all dimensions will come to a very unpleasant and sudden stop.

I just came back from a walk outside, snow under my feet, and it is hard to imagine that only some kilometres below me there is magma in turmoil. Coincidentally, I just read a local success story about heating with geothermal energy in the neighbor town Kitchener which I find quite amazing.

Sometimes I think the English language lacks a dimension because unlike German, nouns have no gender.

The earth as well as nature, energy, science, and also physics are female².

Progress, optimism and change are male³.

The problem is neutral.

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Further Reading:

• Very informative DOE site about Geothermal Power Plants
• More about the Dry Hot Rock power plants
• Brief Intro into Geothermal Energy from RISE - the Research Institute for Sustainable Energy in Australia
• Very readable article in Time Magazine about the power plant in Larderello: Steaming Forward
• Website of the Geothermal Resources Council
• Flashy website from CalEnergy

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Footnote 1: My way of signing the book of condolences for the loss of Hubble's best eye, see posts at Cosmic Variance and Asymptotia.
Footnote 2: So is confusion (die Verwirrung), and stubbornness (die Dickköpfigkeit).
Footnote 3: So is the mistake (der Fehler), and the breakdown (der Zusammenbruch).

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TAGS: SCIENCE, GEOTHERMAL ENERGY, MOTHER EARTH