Comment by leonidasrup
17 hours ago
The Earth's heat content is about 1×10^19 TJ. This heat naturally flows to the surface by conduction at a rate of 44.2 TW and is replenished by radioactive decay at a rate of 30 TW. These power rates are more than double humanity's current energy consumption from primary sources, but most of this power is too diffuse (approximately 0.1 W/m^2 on average) to be recoverable.
In comparison, averaged over the year and the day, the Earth's atmosphere receives 340 W/m^2 from the Sun.
https://en.wikipedia.org/wiki/Solar_irradiance#On_Earth's_su...
This leads naturally to "artificial geothermal", where solar energy is used to heat rocks or soil, and the heat is later extracted. It doesn't have to be anywhere near as deep as ordinary geothermal, which had to accumulate that heat over many thousands of years. Just ~10 meters is about enough.
That's not where natural geothermal energy is from. It's residual heat from planetary formation and some natural radioactivity.
This form of storage also unfortunately only yields heat (via heat pumps or directly), not electricity, as the temperature difference is much too low in comparison to meaningfully run any heat engine from it.
Great if you need to heat houses; not so great if you were hoping to store the solar energy for a rainy, or rather cloudy, day (or night).
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Thanks for that context.
Heat is extracted at geothermal wells much faster than it is being replenished by the average rate of heat flow from the deeper Earth. It's effectively "heat mining". Granted, there's a lot of heat to be mined.