Wednesday, January 31, 2007

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 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 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.

Further Reading:

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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  1. Great idea! Our Big Island of Hawaii gets almost 30% of its energy geothermally. When I see a city the size of San Francisco I will think of that. Perhaps we can connect Earth's internal heat with cosmology.

    What has happened to the Cosmic Variance link?

  2. What has happened to the Cosmic Variance link?

    Not sure. They were having server problems for some while, CPU quota exceeded etc. Half an hour ago I got a funny message telling me to contact the billing department ASAP, so I thought, maybe they haven't paid their bill ;-) Now it's a different error I get, so my guess is it might be a network problem of their provider.

  3. This is a great post! One of the advantages of being married to a HVAC (heating, ventilation, air conditioning) expert is that I learn about the different technologies and which ones are most efficient.

    Our company installs a few "water source" (geothermal) heat pumps a year. Basically, from what I can tell, the apartments that you linked have those. It didn't say exactly if they drilled to ground water or not. But how that works is that you have to drill a well so many feet down (depending on location) to reach the water. The constant temperature of the water assures that you will always be able to extract a certain amount of heat from it. You wouldn't think that you could heat a house with groundwater that is in the 50s F, but you can. Regular heat pumps work the same way but pull the heat out of the air, but since sometimes the air temperature drops below a point of efficient 'heat-grabbing' you have to have "emergency" electric heaters (not separate ones-they are still part of the heat pump unit). Seems like I've heard that the temperature threshold for the air heat pumps is around 28 F, but that could be off.

    The main reason more people don't do the geothermal heat pumps is because of the extra cost, sometimes twice as much as an air heat pump and that takes a long time to make up the difference in lower utility bills.

    Another thing some people worry about is "forced air" systems, but with good filtration your inside forced air can be cleaner than the outside air. Also, back to the ceiling heat, I have to respectfully disagree with the commenter who said it is more efficient than in-floor heat. Radiant floor heating is probably one of the best you can use, and it can also use geothermal heat sources.

    Hey, I really am a file cabinet! ;-)

  4. Oh, yeah, it seems like the German language is very attuned to fundamental realities. ;-)

  5. Thank you, Bee :-)

    that is really great and very informative! I would not have guessed that the US are the biggest user of geothermal energy!

    BTW, the Larderello project - interesting as it is, it does not look very nice in the Tuscan landscape. I have been there once, there are rusty pipelines running all over the coutryside to transport the steam, it looks like a big, extended industrial complex...

    The Basel project, in this respect, seems more promising. It's strange, and a pity, that apparently they didn't properly consider the risk of earthquakes before. When I first heard stories in the news about small earthquakes in the Basel region last December or so, it sounded funny - I guess people living there had a different opinion.

    Heat pumps seem to become more and more popular in Germany - some weeks ago my mother told me that two neighbours had installed such geothermal devides in their gardens and use them for heating and providing hot water. But you still need electric energy to run them.

    This whole energy topic will become extremly important in the next years, I think...

    Cheers, stefan

  6. A comment for the very last of your post - in Sanskrit, fame, beauty, eloquence, memory, intellect, patience and compassion are feminine attributes.

  7. The "H Vac system" is a necessity in "completely enclosed houses" with the construction used in the north. My son uses one.

    While my son was using "in floor heating" as described, you would be amazed at the valving that goes on to different heating sectors of the house.

    Radiant heat is most comfortable I think. My thought have been on more inexpensive ways to maintain the moisture and air in the house, but the filtering forces one to think of more complex system like the H Vac.

    While a boiler is used in my son's case, the idea can be extended as said. I was interested in "wood burning" tied to this system, while he is using natural gas. "In ground circulation" also seems appropriate with regards to this post of Bee's.

    I believe it works on the same principal as creating ice on hockey arenas?

  8. Sorry Bee and Stefan for hijacking your comments here.


    Yeah, there are lots of different ways to get the heat and then to circulate that heat wherever you want it. From what I can tell, here in the US, regional conditions determine the most popular methods. I think in the Northeast they use radiant floor heating and other hot water methods more than here in the South. Of course, in Florida most houses don't have heating systems at all, but only cooling systems.

    You certainly can burn wood to get your heat for hot water and home heating. And recently we've been hearing more about very efficient wood burning systems.

    Also you can use geothermal heat for other things too, like heating a swimming pool. (this is one of my "wish list" items for the future) I'm not sure, but it seems like if you had the money and resources you could build your own geothermal generator for your electicity.

    Not sure about modern ice rinks, but the old rink here uses an ammonia chiller. My husband works on it sometimes too, but I don't really know how it works exactly.

  9. Hi Rae Ann,

    that is really interesting, I had no idea you're an expert on heating :-) Do you think it's possible and realistic that sometime in the future houses can cover their own energy demand. Like, with geothermal support, solar stuff, etc. I know there are some prototypes, but I'm not sure how far this can be pushed, esp. since it crucially depends on the local conditions.

    Please feel free to hijack the comments :-)


  10. Dear Bee,

    another curious coincidence: The February issue of Spektrum der Wissenschaft has a short article about geothermal energy. It is essentially about the Basel project, but it was obviously written before the earthquake trouble...

    Best, stefan

  11. "Do you think it's possible and realistic that sometime in the future houses can cover their own energy demand."

    Yeah, I do, and that it is so dependent on local conditions is kind of a good thing because then people might be more 'attuned' to their local conditions, etc. I don't mean that in a new age hokey way. ;-)

    One of the environmental concerns I have is with water and how too many Americans (and maybe other parts of the world?) are moving to desert areas but expecting to live like they would live in a water-rich area. It kind of turns my stomach to see these lush green golf courses in a desert where they are practically drying up the Colorado River to get that water. To me, this seems more indulgent and wasteful than driving an SUV a few thousand miles a year. ;-)

    There are a lot of people trying to adopt "sustainable" building methods though. It's kind of one of those grassroots movements that will take hold gradually and that usually develops best without too much government interference.

  12. Rae Ann,

    Oh I most defintiely think that innovation in terms of responses to nature can find a more suitable solution to living, then what we construct as stick houses.

    A way to combat "deforestation?"

    Working with stronger abodes while subject to nature's furry? I'll be addressing some of these issues in blog posts later.

    Yes not only "energy conservation" but water too.

    Thanks for info.


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