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Comment by v8xi | Hacker News Reader

I think of geothermal the same way I think of tidal power - seemingly renewable but not really. Harnessing tides dampens the lunar oscillations surprisingly fast (as discussed here: https://news.ycombinator.com/item?id=37383283).

With geothermal, yes there is a huge reservoir of potential energy but speeding up the extraction of this energy is absolutely a terrible idea long term. I'm not gonna rant here, but look at what happened to Mars (only slightly smaller than earth) when the core cooled and the dynamo shut down.

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It's sustainable in the short term (for a very long definitoon of short term) though, which is what really matters wrt migrating off of fossil fuels. We could pull many times humanity's energy consumption from the earth for a century and it would still be a drop in the bucket.

Now, some of these hot spots might not be renewable (in the sense that we drain too much ehat from them and they don't have sufficient heat flux to sustain as much extraction as might seem), but I don't think there's any risk of cooling the core.

See e.g., https://www.wired.com/story/how-long-will-earths-geothermal-...

Yeah the scale of thermal energy contained in the earth makes this fear (prematurely cooling the earth) irrelevant. The entire global consumption of energy is less than 2% of earth's thermal heat flow from the core.

We're at about 40%. Current energy use is 20 TW per year, and the heat capacity of the earth is about 50 TW.

https://en.wikipedia.org/wiki/Watt#Terawatt

Whoops, thanks for the correction. I was looking at end-user electricity consumption so it didn't include all the losses involved.

That's staggering at first glance. So much energy!

But then, I wonder how much it would really matter if we were harvesting that energy to move objects around on earth and turn on LEDs vs letting it dissipate into space. So I'm still skeptical of the concern.

If this is something we actually need to be worried about, why not rant here? I think most people are pretty far from convinced that literally cooling off the earth through geothermal is a possibility we need to be taking seriously.

First comment on the linked article mentions an assumed exponential increase in consumption so the whole thing is moot.

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