Comment by Y-bar
18 hours ago
Can’t speak for large scale sites with abundant volcanic activity… But for residential geothermal the bore hole has a lifetime based on how much ground water there is and how active usage it sees.
This is because using it cools the hole slowly and after a few decades (depending on how quickly ground water can dissipate heat gradient) a new hole need to be drilled a distance away.
Can we cycle the holes? Use one while the other one is warming back up.
There are some modern heat pumps which can put heat energy back into the hole during the warmer season when the pump acts as a (cooler). For my own Daikin pump this would be possible if I had a different flooring than wood.
"Unfortunately" I choose wooden flooring on my heated floors. Cooling this means that the I risk condensation due to moisture build-up and therefore a long-term risk of mould. But I have only need of cooling 1-2 months of the year, so it is not a big deal, I can solve it by clever use of insulation instead.
But for those able to use a geothermal pump like this it also has the short-term benefit of increasing the effectiveness of the hole as well.