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Comment by dahfizz | Hacker News Reader

Genuine question: does "cooling" the center of the Earth via geothermal power plants have any sort of ramifications? If we converted to using 100% geothermal power, what kinds of effects would that have on the Earth's core?

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We are operating on such a tiny sliver of the crust that worries about the core temperature are many orders of magnitude away from being a problem.

However, there are some side effects. Iceland heavily invested in geothermal power plants and as a result their natural geysers are dying out. This is also why the US doesn't run geothermal power plants in the Yellowstone caldera, because the danger to the tourism industry outweighs the potential gains, at least for now.

The heat is already escaping at some rate, geothermal power accelerates it a bit.

We drill a few thousand meters into the crust. There's several thousand kilometers of earth below that.

Geothermal concentrates the thermal flux to the geothermal energy site.

What happens in practice is that such sites end up being rate-limited by either the thermal flux of the surrounding rock, in the case of dry holes which are bored and take out heat directly, or by depleting the groundwater and/or hydrothermal reservoir which feeds a "wet" geothermal project (as with California's Geysers).

Dry holes end up having a limited effective life of a few decades, based on what I've seen, after which there's insufficient thermal energy to drive electrical generation (though it may be suitable for other lower-grade heating applications). Wet holes vary in response depending on how rapidly groundwater is replenished. I believe that the Geyers has dried up numerous wells. In places with ample water infiltration (e.g., near coastlines or in wet climates), I speculate that intrusion of fresh cold water might cool the geothermal reservoir somewhat.

But the source heat, which is radiating from the Earth's core though the mantle and crust, has an effectively fixed flux. There's only so much heat radiating outwards, and a few localised pinpricks and steam generators won't effect that measurably. Volcanoes are far larger and similarly have little overall effect.

Yes, but minimal.

The heat is coming out one way or another. It already traveled 6500 km to the surface unaided, we're just helping it up the last 1 km or so. Frankly, I'd be interested if the core would notice an effect from the removal of the Earth's crust in it's entirety. My money is on "no for any human-relavant-timescale."

For reference, the interior of the Earth works out to about 50 TW of heat. Today, humans consume about 20 TW. The Sun delivers 173000 TW.

https://en.wikipedia.org/wiki/Earth%27s_internal_heat_budget

Interesting, thanks! I did not know the eath's core is still generating heat.

Emitting heat technically. Imagine rocks warmed by a fire or those in a sauna, they cool off very, very slowly. At earths core is a giant chunk of super compressed and super heated lead. I don't recall if the core is the size of the moon, but you could imagine a solid ball of lead for your sauna that is the size of the moon and so hot it would melt if it were not under extreme pressure.

Iron and nickel mostly, not lead, AFAIK

My mistake, good correction

There's a nearly-negligible amount of heat being created from simple radioactive decay, but essentially all of the heat is just leftover from the formation of the planet.

Which is just nuts to think about. The core is that hot and it has been for billions of years. Incredible.

The linked wiki article says around 50% of geothermal heat is from radioactive decay

In part with heavy rains, Puna geothermal fracking on Hawaii Island appears likely to be responsible for 2018 eruption.

So no, not 'minimal'.

I had no idea about the Puna geothermal plant! I'll read up on it!

My "minimal" remark was intended as a response to the question of our effect on the Earth's core; I should have made that more clear. I'm sure we'll uncover all manner of consequences to the upper crust.

Having read into your comment a bit, the USGS doesn't agree with you. :(

https://pubs.usgs.gov/of/2020/1017/ofr20201017.pdf

https://earthscience.stackexchange.com/questions/14259/did-t...

When I looked into this the numbers suggested that energy-wise we'd be extracting a drop in the bucket. There are concerns for local effects though (e.g. earthquakes).

Roughly equivalent to the rise in sea level because of displacement from offshore oil drilling platforms and wind turbines. Which is to say, immeasurable.

Geothermal doesn't cool the center of the Earth; it cools the crust around the wells. The effect farther away is miniscule on any reasonable timescale. Think of it as mining crust heat.

It will cool it down. Do it for long enough and the core will solidify with all sorts of dreadful effects.

But there is an awful lot of energy there so I don't think we need worry for a few million years.

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