Comment Re:It doesn't work at scale (Score 2) 37
The problem with "hot rock" is that, while it has incredibly high thermal mass and can retain a lot of heat, the thermal conductivity of rock is very poor - so poor that once you take the heat out, it takes weeks or months to put it back..
Oddly enough, you just described how it might work perfectly if you had a few sites to extract that energy source that’s more dependent on timing than physics.
Extract the energy from “hot rock” when hot. When it cools to a non-optimum temperature, you switch back to primary power and target the next hot site to pull energy from and wait for the first one to heat back up to become an optimized energy source again. Rinse and repeat.
Switch to geothermal sources in times when the primary is more expensive (such as heating costs in winter). Convert to geothermal when you can mimic nature year round and pull the energy effeciently.
Oh, and much like Japan nuclear wont forget tsunamis anytime soon, let us not forget about natural and wild volcanic activity. One cannot over engineer that safety valve enough.