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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 so

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 …

dexwiz 5y ago
Will they “recharge?” If so, on what time scale?
- Faaak 5y ago
  They can either recharge naturally (i.e. with earth conduction), but it takes a lot of time. 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)
  - restalis 5y ago
    The wells would recharge even without Earth's existing surrounding heat reserves. Moon (and Sun) induced tidal forces do manifest not only in the body of water but also in the Earth's crust, and the resulting tension/friction is quite a source of energy/heat.
Chris2048 5y ago
funny question: can they dig deeper basements now?
xscott 5y ago
Conservatively, there's enough heat down there for the current world's energy use for 17 billion years: https://www.wired.com/story/how-long-will-earths-geothermal-energy-last/ 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.
- gelert 5y ago
  No one here is questioning how hot the Earth is, the issue is sustainably accessing it in countries that are less geologically active.
chopin 5y ago
And, done wrong did a great deal of damage to buildings (Staufen im Breisgau, https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal_drilling_controversy https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal...).
pjc50 5y ago
> The first geothermal wells in Germany have exhausted their heat gradient 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-bottom-of-an-oil-well https://www.quora.com/What-is-the-ground-temperature-at-the-...
davewasthere 5y ago
I can't find anything to back this up. If anything, Germany are investing more in geothermal. It's expensive to set up, which is the downside, but it's a great baseload source for power/heat that keeps generating nonstop with minimal operating costs/maintenance for 30-40 years. Nothing about exhausting their heat gradient. https://www.cleanenergywire.org/news/germanys-geothermal-sector-struggling-take https://www.cleanenergywire.org/news/germanys-geothermal-sec...
- diegocg 5y ago
  Heath exhaustion in geothermal definitely exists. Even wikipedia mentions it > 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.
audunw 5y ago
From what I’ve heard you just need to let the reservoir “recharge” for about 30 years to get the heat back. So worst case you need to build twice as many geothermal plants. It’s not that different from nuclear power plants that need to be decommissioned after some decades… except you can just leave borehole and reuse it after a couple of decades or so. 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.
Glawen 5y ago
That's the good case, the bad case is when your town crumble like Staufen im breisgau.

dexwiz 5y ago

Will they “recharge?” If so, on what time scale?

Faaak 5y ago
They can either recharge naturally (i.e. with earth conduction), but it takes a lot of time. 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)
- restalis 5y ago
  The wells would recharge even without Earth's existing surrounding heat reserves. Moon (and Sun) induced tidal forces do manifest not only in the body of water but also in the Earth's crust, and the resulting tension/friction is quite a source of energy/heat.

Chris2048 5y ago

funny question: can they dig deeper basements now?

xscott 5y ago

Conservatively, there's enough heat down there for the current world's energy use for 17 billion years: https://www.wired.com/story/how-long-will-earths-geothermal-energy-last/ 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.

gelert 5y ago
No one here is questioning how hot the Earth is, the issue is sustainably accessing it in countries that are less geologically active.

chopin 5y ago

And, done wrong did a great deal of damage to buildings (Staufen im Breisgau, https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal_drilling_controversy https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal...).

pjc50 5y ago

> The first geothermal wells in Germany have exhausted their heat gradient 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-bottom-of-an-oil-well https://www.quora.com/What-is-the-ground-temperature-at-the-...

davewasthere 5y ago

I can't find anything to back this up. If anything, Germany are investing more in geothermal. It's expensive to set up, which is the downside, but it's a great baseload source for power/heat that keeps generating nonstop with minimal operating costs/maintenance for 30-40 years. Nothing about exhausting their heat gradient. https://www.cleanenergywire.org/news/germanys-geothermal-sector-struggling-take https://www.cleanenergywire.org/news/germanys-geothermal-sec...

diegocg 5y ago
Heath exhaustion in geothermal definitely exists. Even wikipedia mentions it > 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.

audunw 5y ago

From what I’ve heard you just need to let the reservoir “recharge” for about 30 years to get the heat back. So worst case you need to build twice as many geothermal plants. It’s not that different from nuclear power plants that need to be decommissioned after some decades… except you can just leave borehole and reuse it after a couple of decades or so. 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.

Glawen 5y ago

That's the good case, the bad case is when your town crumble like Staufen im breisgau.