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Is possible to have a geothermal plant (not necessary a very powerful one) to work for several millennia without the place where it is built over running out of heat?

I found a page (don't remember which one) which said that a geothermal plant can only work for around 200 years before it depletes the "heat well".

But (this is my idea) if a geothermal plant was over a "heat river" (a place where lava or magma moved around and heating the area, I don't know if that is possible) the plant could get an endless supply of heat (I don't know if it can recycle water but also there could be a river near!). But after thinking of that I got this question: Would the magma river disappear naturally after several millennia (maybe 10,000 years)? Continents move a few centimetres per year, maybe magma do the same and the river would disappear.

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  • $\begingroup$ Long before your geothermal plant ran out of energy to harness it will have broken (within ~100 years), unless of course there was people around maintaining it. $\endgroup$ – AngelPray Jul 23 '17 at 1:36
  • $\begingroup$ mineral build up clogging pipes is an issue on that time span, even assuming you have frictionless bearings. $\endgroup$ – John Jul 23 '17 at 1:47
  • $\begingroup$ @AngelPray That isn't an issue, I am thinking about a very advanced race, they could fix that. $\endgroup$ – Ender Look Jul 23 '17 at 2:51
  • $\begingroup$ @John, Are you talking about the materials which is made the Geothermal Plant? I have no problem of using fiction-elements, I only care about the ground. $\endgroup$ – Ender Look Jul 23 '17 at 2:52
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    $\begingroup$ That 200 years number is complete nonsense, pseudoscientific babble. $\endgroup$ – Karl Jul 23 '17 at 6:45
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It is feasible that a geothermal power plant could be built that ran and lasted for ten millennia.

On the engineering side it would have to be an extremely robust and readily repairable piece of technology. The subterranean parts of the plant would need to be accessible to robotic repair and maintenance systems. Currently we don't have exactly that level of robotics, but that is not inconceivable that it could be developed in future.

Of course, anyone, nation or power company, wanting to build a ten millennia lifespan geothermal power plant would invest in the necessary technology to keep it working for that duration. This will be extremely difficult to achieve, but it's not impossible. Also, the repair and maintenance robotic technology can be expected to improve during its operating life.

Are there any problems with maintaining a source of geothermal energy? The answer to that is simply no.

Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.

Almost everywhere, the shallow ground or upper 10 feet of the Earth's surface maintains a nearly constant temperature between 50° and 60°F (10° and 16°C). Geothermal heat pumps can tap into this resource to heat and cool buildings. A geothermal heat pump system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow ground near the building. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger. The heat removed from the indoor air during the summer can also be used to provide a free source of hot water.

If the hypothetical ten millennia geothermal power plant uses hot dry rocks as its source of heat, they are not only ubiquitous but it would guarantee a constant power supply. This technology is in its infancy, but the builders of a ten millennia geothermal energy system will have developed it because of its reliability and stability as a power source.

Hot dry rock resources occur at depths of 3 to 5 miles everywhere beneath the Earth's surface and at lesser depths in certain areas. Access to these resources involves injecting cold water down one well, circulating it through hot fractured rock, and drawing off the heated water from another well. Currently, there are no commercial applications of this technology. Existing technology also does not yet allow recovery of heat directly from magma, the very deep and most powerful resource of geothermal energy.

The concept is feasible, doable though not now but certainly in future, and offers long-term stability and reliability as an energy source.

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  • $\begingroup$ Great! The technology isn't an issue I was thinking about a very advanced race!. $\endgroup$ – Ender Look Jul 23 '17 at 2:46
  • $\begingroup$ @EnderLook It turns out the geology is in your favour. Given they have the technology, then the rest is straightforward. $\endgroup$ – a4android Jul 23 '17 at 4:26
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From my understanding of geology, the answer is Yes. This is, of course, discounting anything to do with maintaining the facility over such a time period.

The biggest issue that I can see is plate tectonics. Hawaii is/was formed by a hotspot in the plate, which moves while the islands themselves don't. Some places have volcanoes being active for thousands of years, while others end up going dormant because the source ends up moving. As far as I know, the same applies to most sources of geothermal energy.

Depending on your setting, this could be a non-issue. A place like Mars doesn't have tectonic plates like Earth does, so could easily provide heat for a significant period of time.

The geothermal plant isn't going to suck the heat out of the crust. There's far, far too much heat being produced that a geothermal plant could remove it. But the source of heat won't be still, which is where I think the 200 year note comes from.

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If you can make your power plant to run maintenance-free, it will work forever, that is until geological changes destroy it or remove the heat source. Could happen in 1000 or in a million years.

If you want to play it safe, take a place without some special heat source, some location which has been geologically stable for millions of years. In 1 meter depth, the earth has the local yearly average temperature, and from there on, the thermometer rises 1°C every 30 meters (approximately, until you reach the mantle in ~400 km depth).

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I remember reading an article in Scientific American or New Scientist (can't recall) which described an interesting geothermal type of power plant setup. Apparently there is a currently-living scientist-engineer who has designed a heat-exchange-based system using the temperature differences at the surface and the bottom of the ocean.

Effectively it's just a huge pipe reaching to the bottom of the ocean, which uses the temperature differential to cause an exchange flow. That temperature difference is significant, as long as the sun continues shining. Very few moving parts. It might work for your duration needs.

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