3 ms·

It's not a tunnel, it's a borehole; and therein lies the problem with geothermal power. The usable energy is proportional to the cross-section of the borehole.

It's not a tunnel, it's a borehole; and therein lies the problem with geothermal power. The usable energy is proportional to the cross-section of the borehole. That's just the beginning of the issues, e.g. the magma chamber recedes or it blows out your facility. There are good reasons geothermal only accounts for a small fraction of worldwide energy sources.

mmbop 3y ago
Is this statement just a feeling, or is this coming from a source? I would bet that lots of very smart people have looked at the problem and thought it was viable if they’re moving forward. Also, the people in Iceland are very adept at geothermal (but maybe not this type).
- jackfoxy 3y ago
  It comes from having researched the GeoThermal market to determine whether the last software company I worked for should enter that market. The answer was a resounding NO.
  - jackfoxy 3y ago
    To be clear. Geothermal is great in some places and circumstances. It will never be a big enough world-wide market in the foreseeable future to move the needle much in proportion of total energy produced.
  - mmbop 3y ago
    [dead]
dmoy 3y ago
There's a sibling comment asking for a source, which I can't reply to for some reason. I can't speak to the receding magma or facilities damage, but "proportional to the cross-section of the borehole" is just like first year thermodynamics. If someone has more familiarity with electricity (I guess common on HN?), here's a reasonable introduction to the comparison to circuitry: https://lpsa.swarthmore.edu/Systems/Thermal/SysThermalElem.html https://lpsa.swarthmore.edu/Systems/Thermal/SysThermalElem.h...
- mmbop 3y ago
  Oh yeah - my comment was more about magma spewing out if the chamber grew. I’m really curious about the mechanics of that process. To me, it seems like the magma would could enough/create enough friction in a small borehole to prevent catastrophic failure. However, that’s just a feeling & I’d love to read more about this.
pixl97 3y ago
>The usable energy is proportional to the cross-section of the borehole I mean we thought oil the same way until we developed fracking. While it's not likely a 1:1 relationship with fracking, I'm sure some clever geologists/drilling experts could massively increase the surface area available for heating given the right incentives. As for facilities, the volcano eruption rate is rather low on human timescales, especially for effusive eruptions that don't tend to blow the entire area to bits. Getting 50-100 years between eruptions that could possibly total the facility is likely worth it as you don't have a direct fuel cost.
- jackfoxy 3y ago
  What? No. It's how much fluid (not how much heat) and the oil cut of the fluid you are pumping up the borehole in the O&G industry. This has no bearing on whether the hole is fracked. It's a matter of the decline curve of the well. Not every well in amenable to fracking, and there are techniques other that fracking that will lift the decline curve, but then it starts declining again. But this is neither here nor there. The energy you extract from a geothermal well is heat, which then needs to be converted to electricity. The BTUs in a good oil or gas well exceed those of a geothermal well. You have the same issues of the well becoming less productive. The remediation strategies for this are similar, i.e. pumping fluid back into the ground.

mmbop 3y ago

Is this statement just a feeling, or is this coming from a source? I would bet that lots of very smart people have looked at the problem and thought it was viable if they’re moving forward. Also, the people in Iceland are very adept at geothermal (but maybe not this type).

jackfoxy 3y ago
It comes from having researched the GeoThermal market to determine whether the last software company I worked for should enter that market. The answer was a resounding NO.
- jackfoxy 3y ago
  To be clear. Geothermal is great in some places and circumstances. It will never be a big enough world-wide market in the foreseeable future to move the needle much in proportion of total energy produced.
- mmbop 3y ago
  [dead]

dmoy 3y ago

There's a sibling comment asking for a source, which I can't reply to for some reason. I can't speak to the receding magma or facilities damage, but "proportional to the cross-section of the borehole" is just like first year thermodynamics. If someone has more familiarity with electricity (I guess common on HN?), here's a reasonable introduction to the comparison to circuitry: https://lpsa.swarthmore.edu/Systems/Thermal/SysThermalElem.html https://lpsa.swarthmore.edu/Systems/Thermal/SysThermalElem.h...

mmbop 3y ago
Oh yeah - my comment was more about magma spewing out if the chamber grew. I’m really curious about the mechanics of that process. To me, it seems like the magma would could enough/create enough friction in a small borehole to prevent catastrophic failure. However, that’s just a feeling & I’d love to read more about this.

pixl97 3y ago

>The usable energy is proportional to the cross-section of the borehole I mean we thought oil the same way until we developed fracking. While it's not likely a 1:1 relationship with fracking, I'm sure some clever geologists/drilling experts could massively increase the surface area available for heating given the right incentives. As for facilities, the volcano eruption rate is rather low on human timescales, especially for effusive eruptions that don't tend to blow the entire area to bits. Getting 50-100 years between eruptions that could possibly total the facility is likely worth it as you don't have a direct fuel cost.

jackfoxy 3y ago
What? No. It's how much fluid (not how much heat) and the oil cut of the fluid you are pumping up the borehole in the O&G industry. This has no bearing on whether the hole is fracked. It's a matter of the decline curve of the well. Not every well in amenable to fracking, and there are techniques other that fracking that will lift the decline curve, but then it starts declining again. But this is neither here nor there. The energy you extract from a geothermal well is heat, which then needs to be converted to electricity. The BTUs in a good oil or gas well exceed those of a geothermal well. You have the same issues of the well becoming less productive. The remediation strategies for this are similar, i.e. pumping fluid back into the ground.