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What does drilling a Hole for Water cost here in Europe?
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Siwastaja:

--- Quote from: Someone on March 23, 2022, 09:08:10 pm ---Which is (almost certainly) using the ground not as an energy source but as a thermal (energy) storage/"infinite" heatsink, that works great in isolated/sparse areas where the climate annually averages around the "comfortable" indoor temperature.

--- End quote ---

Exactly.

I don't personally like to use the word "geothermal" because it's confusing and used for different energy sources. Ground-source heatpumping can tap two different sources:
1) Actual geothermal, i.e., heat flow from the molten core of the Earth (by just drilling far enough, or utilizing natural hot water sources). Actual energy source is the massive pool of molten lava, since the Earth was born.
2) Just the thermal storage capacity of the soil or bedrock pretty close to the surface, deep enough so that it follows yearly average climate temperature. Actual energy source is the Sun.

In Northern Finland for example, where air-source heatpumping gets impractical due to significant periods of time below say -20degC air temperature, ground source heatpump installations are used; this would be typically a 150-meter deep well, maybe a bit more. Drilling cost is roughly around 10k€. AFAIK, this is deep enough that the actual geothermal (the lava thing!) shows a tiny contribution, but still it's mostly just averaging the yearly climate, i.e., solar power. Which would be something like +5degC in those areas. Way better for heatpumping than -30degC air!

Accumulating snow works like thermal insulation during winter, so the soil/bedrock temperature is tad higher than you could guesstimate from the yearly average air temperature. So the idea is, maybe the well drilled in bedrock is at +7degC when you start using it during the fall, and maybe it's down to +2degC when you are done in the spring. Then it regenerates for the next winter.

For the energy to regenerate (i.e., the soil needs to heat up again during summer), the well needs to be deep enough, or you need two in parallel, and can't just place them close to each other. Due to the required gaps, this is not THE solution for global energy problems, but it can of course be a small part of it, in sparsely populated, very cold climates - exactly like Northern Finland.

Then again, "true" geothermal works best in areas where you naturally get access to the heated water (hot springs). There, you don't even need heatpumping; temperature could be high enough for passive energy transfer, just pump the water through heat exchangers. It's obvious to utilize this resource to the fullest if you have it, but 99.9999% of people on the planet just won't.
NiHaoMike:

--- Quote from: Someone on March 24, 2022, 07:07:10 am ---Short answer is practical storage lifetimes are months/seasonal, and real sites observe this along with changes in ground temperature on the time scales of years:
"Evaluation of Ground Temperature Changes by the Operation of the Geothermal Heat Pump System and Climate Change in Korea"
https://www.mdpi.com/2073-4441/12/10/2931/htm
Put too many users with imbalanced energy demands in the ground and it will cook or freeze (depending on which direction you push the energy), hence it only being practical if balanced or sparse/selfish/tragedy of the commons/ignoring externalities/short term (the opposite of sustainable).

--- End quote ---
Seems like it should be pretty straightforward to make it balanced if it's well into months or years, use solar thermal collectors to add heat where there's more heating demand than cooling, use radiators to remove heat where there's more cooling demand than heating.
Someone:

--- Quote from: NiHaoMike on March 25, 2022, 04:24:36 am ---
--- Quote from: Someone on March 24, 2022, 07:07:10 am ---Short answer is practical storage lifetimes are months/seasonal, and real sites observe this along with changes in ground temperature on the time scales of years:
"Evaluation of Ground Temperature Changes by the Operation of the Geothermal Heat Pump System and Climate Change in Korea"
https://www.mdpi.com/2073-4441/12/10/2931/htm
Put too many users with imbalanced energy demands in the ground and it will cook or freeze (depending on which direction you push the energy), hence it only being practical if balanced or sparse/selfish/tragedy of the commons/ignoring externalities/short term (the opposite of sustainable).

--- End quote ---
Seems like it should be pretty straightforward to make it balanced if it's well into months or years, use solar thermal collectors to add heat where there's more heating demand than cooling, use radiators to remove heat where there's more cooling demand than heating.

--- End quote ---
Hence the free-rider problem if they are densely installed, someone needs to install infrastructure and operate it to do the balancing, but any one individual could just likely ignore it.


--- Quote from: Siwastaja on March 24, 2022, 01:46:41 pm ---1) Actual geothermal, i.e., heat flow from the molten core of the Earth (by just drilling far enough, or utilizing natural hot water sources). Actual energy source is the massive pool of molten lava, since the Earth was born.
--- End quote ---
Yep, and has exactly the same problem of being a largely uncontrolled public good. When people see "free" energy they suck it up and spend it foolishly, leading to overcorrection in the management such as wide scale closure/capping:
"Effects of Bore Closure at Rotorua, New Zealand"
https://www.geothermal-energy.org/pdf/IGAstandard/Japan/1997/Scott.pdf
nctnico:

--- Quote from: Siwastaja on March 24, 2022, 01:46:41 pm ---Then again, "true" geothermal works best in areas where you naturally get access to the heated water (hot springs). There, you don't even need heatpumping; temperature could be high enough for passive energy transfer, just pump the water through heat exchangers. It's obvious to utilize this resource to the fullest if you have it, but 99.9999% of people on the planet just won't.

--- End quote ---
In the end it is a cost versus benefit calculation. You can use geothermal energy in many places; you just need to drill deep enough (2 to 4km) and stay clear from fault lines. In the Netherlands there are about 30 geothermal wells in operation and several  tens more in the planning stage. It looks like most are used to heat greenhouses (to grow crops and flowers) but it could be very useful to heat homes as well through district heating (which is being rolled out in several cities already).
MadScientist:
Well drilling is very common here in Ireland , costs about €3000-€9000 for typical potable water drilling lined , excluding pumps and treatments ,   very  dependant on drilling conditions
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