6 ms·

Is it really necessary to go so deep? Why not start in the foothills of some granitic massif and drill up? I'm sure you'll get lots of heat!

deleted 4y ago
[deleted]
margalabargala 4y ago
It's not that 10 mile holes will be necessary everywhere, it's that "10 miles" is the depth necessary to make these worthwhile anywhere. You don't need to drill 10 miles to get to geothermal temperatures in Iceland, nor in Yellowstone. But you might in Ohio, or Ireland.
- pfdietz 4y ago
  You also don't need to drill so deep if all you're interested in is lower grade heat. For example, at Cornell in Ithaca, NY they've just drilled a 3 km deep hole to evaluate getting heat (at ~90 C) to make hot water for heating the campus.
  - sidewndr46 4y ago
    What was the result of that evaluation?
    - pfdietz 4y ago
      The temperature is high enough; beyond that we haven't heard yet.
      - toomuchtodo 4y ago
        Any paper on this specific initiative? This sounds like a slam dunk for any population center needing district heat.
        pfdietz 4y ago
        Here's a website where they're putting up data from the borehole. https://deepgeothermalheat.engineering.cornell.edu/research/ https://deepgeothermalheat.engineering.cornell.edu/research/ Note the wireline logs. You can see the radioactivity (which is where the heat comes from) go way up as they reach the crystalline basement rocks. The technical issue that's going to determine if this is feasible is how quickly water from an injection well can get to a withdrawal well. This depends on the how fractured the rocks are.
        pfdietz 4y ago
        Also: publications and presentations https://deepgeothermalheat.engineering.cornell.edu/publications-presentations/ https://deepgeothermalheat.engineering.cornell.edu/publicati...
        zokier 4y ago
        Not the same project, but in Otaniemi they drilled 6km to find the project to not work as planned. Unfortunately this was the best article I could find for now: https://www-lansivayla-fi.translate.goog/paikalliset/4558850?_x_tr_sl=fi&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp https://www-lansivayla-fi.translate.goog/paikalliset/4558850...
        pfdietz 4y ago
        > In Finland, the temperature rises by 18 degrees per kilometer. The geothermal gradient at Ithaca is a bit higher than that. Also, correct me if I'm wrong, but isn't Finland mostly underlain at fairly shallow depth by hard crystalline rocks that are more expensive to drill through? At Ithaca, there's a 3 km thickness of sedimentary rocks before hitting that basement rock.
        euroderf 4y ago
        Grossly oversimplified, inland is swamps & lakes atop crystalline rocks, while Helsinki is landfill punctuated by granite outcroppings.

deleted 4y ago

[deleted]

margalabargala 4y ago

It's not that 10 mile holes will be necessary everywhere, it's that "10 miles" is the depth necessary to make these worthwhile anywhere. You don't need to drill 10 miles to get to geothermal temperatures in Iceland, nor in Yellowstone. But you might in Ohio, or Ireland.

pfdietz 4y ago
You also don't need to drill so deep if all you're interested in is lower grade heat. For example, at Cornell in Ithaca, NY they've just drilled a 3 km deep hole to evaluate getting heat (at ~90 C) to make hot water for heating the campus.
- sidewndr46 4y ago
  What was the result of that evaluation?
  - pfdietz 4y ago
    The temperature is high enough; beyond that we haven't heard yet.
    - toomuchtodo 4y ago
      Any paper on this specific initiative? This sounds like a slam dunk for any population center needing district heat.
      - pfdietz 4y ago
        Here's a website where they're putting up data from the borehole. https://deepgeothermalheat.engineering.cornell.edu/research/ https://deepgeothermalheat.engineering.cornell.edu/research/ Note the wireline logs. You can see the radioactivity (which is where the heat comes from) go way up as they reach the crystalline basement rocks. The technical issue that's going to determine if this is feasible is how quickly water from an injection well can get to a withdrawal well. This depends on the how fractured the rocks are.
        pfdietz 4y ago
        Also: publications and presentations https://deepgeothermalheat.engineering.cornell.edu/publications-presentations/ https://deepgeothermalheat.engineering.cornell.edu/publicati...
      - zokier 4y ago
        Not the same project, but in Otaniemi they drilled 6km to find the project to not work as planned. Unfortunately this was the best article I could find for now: https://www-lansivayla-fi.translate.goog/paikalliset/4558850?_x_tr_sl=fi&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp https://www-lansivayla-fi.translate.goog/paikalliset/4558850...
        pfdietz 4y ago
        > In Finland, the temperature rises by 18 degrees per kilometer. The geothermal gradient at Ithaca is a bit higher than that. Also, correct me if I'm wrong, but isn't Finland mostly underlain at fairly shallow depth by hard crystalline rocks that are more expensive to drill through? At Ithaca, there's a 3 km thickness of sedimentary rocks before hitting that basement rock.
        euroderf 4y ago
        Grossly oversimplified, inland is swamps & lakes atop crystalline rocks, while Helsinki is landfill punctuated by granite outcroppings.