5 ms·

Borehole geothermal is possible too. Basically, find a large, hot mass of rock close to the surface, drill down a couple of kilometres, pump water down and get

Borehole geothermal is possible too. Basically, find a large, hot mass of rock close to the surface, drill down a couple of kilometres, pump water down and get steam out (typical temp is ~200-300C). That's in Australia, known for its geological stability, lack of active volcanoes, etc.

jacques_chester 14y ago
In theory. In practice nobody has managed to produce a commercial-scale plant that actually does that. For example: the deeper the borehole, the more noticeable the effect of tectonic drift.
- anthonyb 14y ago
  Drift? Not in Australia. Even in other parts of the world, most of the boreholes are proposed in large granite masses (they're hot because of radioactive decay as well as conduction) which are relatively static. Mostly it's just an issue of getting enough investment to get a plant off the ground - there's no major technical impediment involved.
  - jacques_chester 14y ago
    Yes, even in Australia. We're very stable by geological standards, yet we still have minor fault lines and the whole plate is still moving north. When your borehole is kilometres deep it only takes a tiny amount of drift to start breaking stuff all up and down the system. And superhot steam is not exactly a friendly substance to begin with. The main company who've been working on the Australian deep-drilling geothermal problem is Geodynamics. And they have been at it for years and years. They've consumed tens of millions of dollars and have, so far, not successfully produced a deep-geothermal plant. It's just not as easy as people make out.
    - LockeWatts 14y ago
      >And superhot steam is not exactly a friendly substance to begin with. Don't pretty much all power sources use "superhot" steam to turn turbines? What's special about this steam?
      - jacques_chester 14y ago
        It's dirty. Laugh if you like; but the stuff used in stationary plants isn't full of an unpredictable cocktail of dissolved minerals and hydrocarbons. Truthfully I am not across the detail of the problems with deep boreholes. I am however across the fact that it hasn't worked yet. And we're talking stuff that Very Intelligent People With A Lot Of Funding have been working on for quite a while at this point. And they don't even have a working proof-of-concept plant working yet. Deep borehole geothermal sounds great on paper, but the engineering challenges are enormous and yet to be surmounted. By comparison oil, gas and especially coal are absolute doddles with work with.

jacques_chester 14y ago

In theory. In practice nobody has managed to produce a commercial-scale plant that actually does that. For example: the deeper the borehole, the more noticeable the effect of tectonic drift.

anthonyb 14y ago
Drift? Not in Australia. Even in other parts of the world, most of the boreholes are proposed in large granite masses (they're hot because of radioactive decay as well as conduction) which are relatively static. Mostly it's just an issue of getting enough investment to get a plant off the ground - there's no major technical impediment involved.
- jacques_chester 14y ago
  Yes, even in Australia. We're very stable by geological standards, yet we still have minor fault lines and the whole plate is still moving north. When your borehole is kilometres deep it only takes a tiny amount of drift to start breaking stuff all up and down the system. And superhot steam is not exactly a friendly substance to begin with. The main company who've been working on the Australian deep-drilling geothermal problem is Geodynamics. And they have been at it for years and years. They've consumed tens of millions of dollars and have, so far, not successfully produced a deep-geothermal plant. It's just not as easy as people make out.
  - LockeWatts 14y ago
    >And superhot steam is not exactly a friendly substance to begin with. Don't pretty much all power sources use "superhot" steam to turn turbines? What's special about this steam?
    - jacques_chester 14y ago
      It's dirty. Laugh if you like; but the stuff used in stationary plants isn't full of an unpredictable cocktail of dissolved minerals and hydrocarbons. Truthfully I am not across the detail of the problems with deep boreholes. I am however across the fact that it hasn't worked yet. And we're talking stuff that Very Intelligent People With A Lot Of Funding have been working on for quite a while at this point. And they don't even have a working proof-of-concept plant working yet. Deep borehole geothermal sounds great on paper, but the engineering challenges are enormous and yet to be surmounted. By comparison oil, gas and especially coal are absolute doddles with work with.