alt Hacker NewsThis 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).