I want to believe in GeoThermal. A recent experiment in Australia went bad, this really saddened me because the underlying model clearly works (Iceland, NZ) but something about the combination of drill, frack, extract and process to energy just didn't work out, nor did the post experiment remediation (IIRC)
I also believe, that we actually deplete both deep heat, and deep coolth. Deep heat, you have to keep expanding the deep heat extraction zone or create pumped states in a wider area somehow, Coolth: London underground was lovely and airconditioner cool, it now has 100+ years of soaked in heat and is significantly hotter than it used to be.
The brine in the permeable rock is heated by radiation from the earth's core. It is pumped to surface, power generated, then injected back into the earth at a sufficient distance, so that by the time it flows back to the extraction well it will have been re-heated to the original temperature.
So no, the subsurface will not cool over time (except with some crackpot "technologies" like one mentioned towards the end of the article that rhymes with "never"). It's actually harnessing the radiation of the earth's geology.
There are some places where power is extracted faster than the geology can support. In those cases electrical generation tapers off. This is happening in Turkey for example. But it's because of greed, not because of anything inherent in the technology.
I was (I think) referring to the cooper basin project. It was non-viable on LCOE given transmission costs and rate of extraction. I can't find the remediation story links, maybe confused this with other energy/fracking problems, but the do note the fracks made mag 3.7 earthquakes, which may have been played up as a risk-side problem.
Thanks. I thought it was that some prior radiative heat was being consumed, and wasn't being refreshed by deep water brine. Maybe thats what you said: the rate of extraction can exceed the rate of renewal?
I also believe, that we actually deplete both deep heat, and deep coolth. Deep heat, you have to keep expanding the deep heat extraction zone or create pumped states in a wider area somehow, Coolth: London underground was lovely and airconditioner cool, it now has 100+ years of soaked in heat and is significantly hotter than it used to be.