The first geothermal wells in Germany have exhausted their heat gradient; after less than 30 years … so, unless you’re actually in Iceland or the Canaries or something similar, this might not even sustainable for even one full generation …
The first hit on google for this phrase is .. this comment, so could you provide a less circular citation please? :)
I do understand that all heat is local, you cannot extract heat faster than it can flow to the point of extraction, which is dependent on the R value of the rock and whether you've drilled into a liquid area or not.
(I wonder if there are some oil fields that have high enough below-ground temperatures to be worth using for this? The drilling is done, a sunk cost, and the wells produce mostly dirty water)
https://www.quora.com/What-is-the-ground-temperature-at-the-...
It’s also better than drilling for oil/gas.. where you need to keep drilling constantly to get more oil/gas.
And as some here have pointed out, if there’s an excess of energy, which there will often be in a world with lots of renewables, you can pump heat back down into the reservoir, extending its lifetime.
So as always, at just comes down to cost. And I truly believe that if we put as much money into geothermal as we have with fossil fuels and nuclear power, it’ll be the cheapest and most environmentally friendly way of making power in a decade or two.
Or you can also recharge them during the summer, either with solar thermal panels, or on a small measure, by running your HVAC "backwards" (i.e. cooling your home and thus heating the wells)
https://www.cleanenergywire.org/news/germanys-geothermal-sec...
> Even though geothermal power is globally sustainable, extraction must still be monitored to avoid local depletion.[21] Over the course of decades, individual wells draw down local temperatures and water levels until a new equilibrium is reached with natural flows. The three oldest sites, at Larderello, Wairakei, and the Geysers have experienced reduced output because of local depletion. Heat and water, in uncertain proportions, were extracted faster than they were replenished. If production is reduced and water is reinjected, these wells could theoretically recover their full potential. Such mitigation strategies have already been implemented at some sites.
I assume that some of the places with the largest geothermal investments (ie. Iceland) don't suffer this problem that much.
https://www.wired.com/story/how-long-will-earths-geothermal-...
Considering our sun will explode in 5.5 billion years, that should be good enough.