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I'd be careful about getting too optimistic. Conventional geothermal is about 4-5 cents/kWh, on par with natural gas in the US. The dominant capital cost is dr

I'd be careful about getting too optimistic. Conventional geothermal is about 4-5 cents/kWh, on par with natural gas in the US. The dominant capital cost is drilling a large well (you need volume), and so geothermal plants are generally only built in areas that require shallow (1km) wells. Well costs are ~quadratic in depth. Given how much money has already been spent optimizing drilling for the oil&gas industry, along with how cutthroat that market is, I don't see the cost coming down significantly. As a result, deep geothermal will likely be limited to niche regions like Iceland. And you need deep geothermal to scale it past the existing locations. I would love to be wrong, since geothermal checks all the boxes for renewables and is also suitable for base load power, but I don't see an obvious path forward short of a drilling tech miracle. (source: Climate and Energy R&D group)

phreeza 9y ago
A bit late to the party but i wanted to back this up by linking to the relevant chapter from the fantastic book by David MacKay: http://withouthotair.com/c16/page_96.shtml http://withouthotair.com/c16/page_96.shtml The chapter is only 4 pages long and he quickly works out that if done sustainably, even blanketing the entire country with geothermal plants could provide at most 2 kWh/day per person in the UK. Current consumption is about 125 kWh/day per person. So even without the capex argument, it is just not a very efficient source of energy long-term.
- therealdrag0 9y ago
  Your statement should be qualified with "for the UK region". > Other places in the world have more promising hot dry rocks, so if you want to know the geothermal answers for other countries, be sure to ask a local. But sadly for Britain, geothermal will only ever play a tiny part.
gtvwill 9y ago
It can get pretty crazy the resources consumed by a drill rig during the average week drilling. New bits, roughly 1200 or so liters of fuel every 24 hours, all kinds of sacrificial bits of tube if they are core drilling their holes. Any hundreds of liters of drilling fluids depending on down hole conditions. I was blown away by the consumption when I saw it first hand. The fuel and drilling bits were the craziest. Then all of the maintenance consumables that you go through as a result of running 24/7. I shudder to consider the quantities of hardware consumed to drill 4km+ you would get all kinds of crazy hard rock down there, not to mention the time it would take for rod pulls.
lumost 9y ago
Has the lifetime of deep GeoThermal wells been studied at all? Unlike oil/natural gas drilling, a deep geothermal well should provide energy indefinitely barring collapse or obstruction of the well. I'd venture the cost of shutdown and clearing obstructions is fairly low relative to the initial CapEx of the well.
- chris_va 9y ago
  Yes, most wells are productive for about 30 years, and then you have to wait a bit (another 30) to let the rock heat back up. The NPV past 60 years is pretty tiny, so it is hard to amortize capex that far out. Worst case, you run them continuously at half capacity, but then your cost per kWh is about 2x.
  - xoa 9y ago
    >Yes, most wells are productive for about 30 years Wait, I haven't looked at geothermal in a long time so I'm not at all up to speed on the current state of the at. But previously you wrote: >and so geothermal plants are generally only built in areas that require shallow (1km) wells That sounds like your "30 years" number there is for shallow wells. Intuitively it doesn't seem like this logic would necessarily be identical for deeper wells: obviously at some depth the rock is always extremely hot (or, in fact, molten). The article seems to indicate that they expect a deeper well to produce higher temperatures and pressures, in turn allowing more energy production, and that seems like it'd make sense. Maybe 1km vs 5km makes no difference in lifetime beyond that, but does your analysis include deep wells already in an equivalent area? Otherwise it doesn't seem reasonable to extrapolate past lifetimes of shallow wells to future lifetimes of deep wells, even ignoring that they say they'll be able to achieve far higher energy generation per well.
    - BurningFrog 9y ago
      > obviously at some depth the rock is always extremely hot Not if you keep pumping in water to run a steam turbine. I assume that's how geothermal energy works, and I'm not going to double check.
arca_vorago 9y ago
I think the real approach to geo should be more focused on decentralized use, instead of trying to do big arrays of holes, like solar, it's in the combination with localization of other technologies in array themselves that seem to offer the most opportunity. Wind, solar, geo... they all work together better than as a single unit.
- chris_va 9y ago
  That is sort of true from a grid perspective, but the math doesn't really work out well for geothermal. Geothermal has high capex, low opex, so you need it running 24/7 to amortize the high capital costs. If you combine it with renewables, you get high fluctuation of demand from the grid, which selects for the exact opposite technology (higher opex, lower capex). Natural gas fits the bill, so that is where the market is going.
Rabei 9y ago
The additional advantage of Geotermal from an operations standpoint it has 0 marginal cost which guarantees it will be producing on most economically dispatched power grids.
BurningFrog 9y ago
> deep geothermal will likely be limited to niche regions like Iceland True, but aren't there plenty of such regions around the world? In the US I can think of at least Hawaii and Yellowstone. Not the greatest population centers, but power lines have a good range. Also, Iceland is making good use of its comparative advantage by doing power intensive production like aluminum smelting and bitcoin mining.
- GregBuchholz 9y ago
  What about the west coast volcanoes in North America? https://en.wikipedia.org/wiki/List_of_Cascade_volcanoes https://en.wikipedia.org/wiki/List_of_Cascade_volcanoes ...how deep do you have to go to get to the 400C temperature level on some of those volcanoes??
  - esterly 9y ago
    DuckDuckGo for Cascades Fumaroles. You can hike to vents emitting steam, many through glaciers. http://www.ivm-fund.org/mount-baker-volcano-fumaroles/ http://www.ivm-fund.org/mount-baker-volcano-fumaroles/ Also many hot springs could be potential GeoThermal candidate areas http://www.hotspringsenthusiast.com/USsprings.asp http://www.hotspringsenthusiast.com/USsprings.asp
  - BurningFrog 9y ago
    The world's largest geothermal energy field is in California, 1½ hour north of San Francisco: https://en.wikipedia.org/wiki/The_Geysers https://en.wikipedia.org/wiki/The_Geysers
- sudojudo 9y ago
  Imagine the political/public outrage around building an alternative energy source in Yellowstone National Park. People on both sides of the aisle would be losing their minds. That said, geothermal activity isn't confined to the park borders, and there may be a suitable spot outside of the park. But again, politics. Building a geothermal plant in the middle of natural gas country would be a challenge. Small note about Iceland- My web host (1984) is located there, and the servers run on 100% geothermal. That, in combination with the stellar privacy laws, make Iceland a nice fit for me.
GregBuchholz 9y ago
>Well costs are ~quadratic in depth. Anyone know as to why this is the case? At first pass it seems like your cutting tools should wear out in proportion to depth. But I suppose as things get warmer tool wear becomes faster. What types of tool materials are used for rock boring? Diamond? Tungsten carbide? Is is more of a "conventional machining" process, or an abrasive / water jet? Or explosive like in hard rock mining? What else has an effect on cost for deep holes? Shaft length gets longer, so the twist becomes more of a problem if your are driving rotating bits from the top? Does it have to do with removing the material from the bottom of the hole to the top? Others?
- cnnsucks 9y ago
  "Anyone know as to why this is the case?" Think of a telescopic antenna. That structure is similar to what is done to bore a well. You start with large casing diameter and add progressively smaller casings until you reach the target depth. The deeper you go the bigger the casing you must start with. Offshore deep water stuff can be a meter in diameter with 10cm solid steel walls; monstrously heavy and costly materials. And you use kilometers of the stuff. There are a lot of reasons why costs scale as they do with depth; casing is just one of the more obvious.
  - GregBuchholz 9y ago
    Anyone recommend a good pop-sci book on deep hole boring? Seems like it could be an interesting light engineering read.
  - lumost 9y ago
    For deep wells would the need for casing change depending on the material you're drilling into? once your into hard granite bedrock I'd imagine wells of a certain diameter are stable with minimal to no casing.
    - cnnsucks 9y ago
      Yes, geology is a big factor in engineering a well. Pressure is another. Every well is engineered to the prevailing conditions and requirements. Sometimes it is possible to elide heavy casing which can save large amounts of money.
abalone 9y ago
> geothermal checks all the boxes for renewables Article: "Although geothermal energy is still preferable to gas, coal and oil, it's not 'completely renewable and without problems... As soon as you start drilling you have issues to it, such as sulphur pollution and CO2 emission...'"
Beltiras 9y ago
Don't bill deep geothermal as any sort of green. There are usually emissions that have health consequences for the population around the power plant. The corrosion of the pipes bringing steam from the drill site to the turbines is massive. Drilling that deep and pumping water into the hole ups the risk of earthquakes. (source: I live in Reykjavík and have witnessed first-hand the increased stench from the Hellisheiði geothermal plant)
- RealityVoid 9y ago
  DISCLAIMER: I'm not an expert in this and I can be very off concerning this area. Having said this, I think the risk of man-made earthquakes is exaggerated. I mean, I think it might be possible to trigger small seismic events, but they should not be the destructive kind. I doubt we can trigger massive destructive eathquakes like this. Also, from what I understand, smaller seismic evnts should lower the energy that the bigger ones have.
  - Beltiras 9y ago
    Tell that to the people of Selfoss and Hveragerði which have now become accustomed to smaller quakes on a more regular basis than usually in the past.
    - RealityVoid 9y ago
      Is it damaging though? That is the question I want answered. I mean, even in my post, I did not question the presence of more frequent small earthquakes, I questioned if these earthquakes are any sort of real issue that produces damages or simply unfounded panic.
      - Beltiras 9y ago
        Not being able to trust that the ground you stand on won't shake violently? Are you being serious?
        9y ago
fulafel 9y ago
Natural gas use will need to stop because of co2. IOW that "on par" cost of NG unsustainably excludes externalities.

phreeza 9y ago

A bit late to the party but i wanted to back this up by linking to the relevant chapter from the fantastic book by David MacKay: http://withouthotair.com/c16/page_96.shtml http://withouthotair.com/c16/page_96.shtml The chapter is only 4 pages long and he quickly works out that if done sustainably, even blanketing the entire country with geothermal plants could provide at most 2 kWh/day per person in the UK. Current consumption is about 125 kWh/day per person. So even without the capex argument, it is just not a very efficient source of energy long-term.

therealdrag0 9y ago
Your statement should be qualified with "for the UK region". > Other places in the world have more promising hot dry rocks, so if you want to know the geothermal answers for other countries, be sure to ask a local. But sadly for Britain, geothermal will only ever play a tiny part.

gtvwill 9y ago

It can get pretty crazy the resources consumed by a drill rig during the average week drilling. New bits, roughly 1200 or so liters of fuel every 24 hours, all kinds of sacrificial bits of tube if they are core drilling their holes. Any hundreds of liters of drilling fluids depending on down hole conditions. I was blown away by the consumption when I saw it first hand. The fuel and drilling bits were the craziest. Then all of the maintenance consumables that you go through as a result of running 24/7. I shudder to consider the quantities of hardware consumed to drill 4km+ you would get all kinds of crazy hard rock down there, not to mention the time it would take for rod pulls.

lumost 9y ago

Has the lifetime of deep GeoThermal wells been studied at all? Unlike oil/natural gas drilling, a deep geothermal well should provide energy indefinitely barring collapse or obstruction of the well. I'd venture the cost of shutdown and clearing obstructions is fairly low relative to the initial CapEx of the well.

chris_va 9y ago
Yes, most wells are productive for about 30 years, and then you have to wait a bit (another 30) to let the rock heat back up. The NPV past 60 years is pretty tiny, so it is hard to amortize capex that far out. Worst case, you run them continuously at half capacity, but then your cost per kWh is about 2x.
- xoa 9y ago
  >Yes, most wells are productive for about 30 years Wait, I haven't looked at geothermal in a long time so I'm not at all up to speed on the current state of the at. But previously you wrote: >and so geothermal plants are generally only built in areas that require shallow (1km) wells That sounds like your "30 years" number there is for shallow wells. Intuitively it doesn't seem like this logic would necessarily be identical for deeper wells: obviously at some depth the rock is always extremely hot (or, in fact, molten). The article seems to indicate that they expect a deeper well to produce higher temperatures and pressures, in turn allowing more energy production, and that seems like it'd make sense. Maybe 1km vs 5km makes no difference in lifetime beyond that, but does your analysis include deep wells already in an equivalent area? Otherwise it doesn't seem reasonable to extrapolate past lifetimes of shallow wells to future lifetimes of deep wells, even ignoring that they say they'll be able to achieve far higher energy generation per well.
  - BurningFrog 9y ago
    > obviously at some depth the rock is always extremely hot Not if you keep pumping in water to run a steam turbine. I assume that's how geothermal energy works, and I'm not going to double check.

arca_vorago 9y ago

I think the real approach to geo should be more focused on decentralized use, instead of trying to do big arrays of holes, like solar, it's in the combination with localization of other technologies in array themselves that seem to offer the most opportunity. Wind, solar, geo... they all work together better than as a single unit.

chris_va 9y ago
That is sort of true from a grid perspective, but the math doesn't really work out well for geothermal. Geothermal has high capex, low opex, so you need it running 24/7 to amortize the high capital costs. If you combine it with renewables, you get high fluctuation of demand from the grid, which selects for the exact opposite technology (higher opex, lower capex). Natural gas fits the bill, so that is where the market is going.

Rabei 9y ago

The additional advantage of Geotermal from an operations standpoint it has 0 marginal cost which guarantees it will be producing on most economically dispatched power grids.

BurningFrog 9y ago

> deep geothermal will likely be limited to niche regions like Iceland True, but aren't there plenty of such regions around the world? In the US I can think of at least Hawaii and Yellowstone. Not the greatest population centers, but power lines have a good range. Also, Iceland is making good use of its comparative advantage by doing power intensive production like aluminum smelting and bitcoin mining.

GregBuchholz 9y ago
What about the west coast volcanoes in North America? https://en.wikipedia.org/wiki/List_of_Cascade_volcanoes https://en.wikipedia.org/wiki/List_of_Cascade_volcanoes ...how deep do you have to go to get to the 400C temperature level on some of those volcanoes??
- esterly 9y ago
  DuckDuckGo for Cascades Fumaroles. You can hike to vents emitting steam, many through glaciers. http://www.ivm-fund.org/mount-baker-volcano-fumaroles/ http://www.ivm-fund.org/mount-baker-volcano-fumaroles/ Also many hot springs could be potential GeoThermal candidate areas http://www.hotspringsenthusiast.com/USsprings.asp http://www.hotspringsenthusiast.com/USsprings.asp
- BurningFrog 9y ago
  The world's largest geothermal energy field is in California, 1½ hour north of San Francisco: https://en.wikipedia.org/wiki/The_Geysers https://en.wikipedia.org/wiki/The_Geysers
sudojudo 9y ago
Imagine the political/public outrage around building an alternative energy source in Yellowstone National Park. People on both sides of the aisle would be losing their minds. That said, geothermal activity isn't confined to the park borders, and there may be a suitable spot outside of the park. But again, politics. Building a geothermal plant in the middle of natural gas country would be a challenge. Small note about Iceland- My web host (1984) is located there, and the servers run on 100% geothermal. That, in combination with the stellar privacy laws, make Iceland a nice fit for me.

GregBuchholz 9y ago

>Well costs are ~quadratic in depth. Anyone know as to why this is the case? At first pass it seems like your cutting tools should wear out in proportion to depth. But I suppose as things get warmer tool wear becomes faster. What types of tool materials are used for rock boring? Diamond? Tungsten carbide? Is is more of a "conventional machining" process, or an abrasive / water jet? Or explosive like in hard rock mining? What else has an effect on cost for deep holes? Shaft length gets longer, so the twist becomes more of a problem if your are driving rotating bits from the top? Does it have to do with removing the material from the bottom of the hole to the top? Others?

cnnsucks 9y ago
"Anyone know as to why this is the case?" Think of a telescopic antenna. That structure is similar to what is done to bore a well. You start with large casing diameter and add progressively smaller casings until you reach the target depth. The deeper you go the bigger the casing you must start with. Offshore deep water stuff can be a meter in diameter with 10cm solid steel walls; monstrously heavy and costly materials. And you use kilometers of the stuff. There are a lot of reasons why costs scale as they do with depth; casing is just one of the more obvious.
- GregBuchholz 9y ago
  Anyone recommend a good pop-sci book on deep hole boring? Seems like it could be an interesting light engineering read.
- lumost 9y ago
  For deep wells would the need for casing change depending on the material you're drilling into? once your into hard granite bedrock I'd imagine wells of a certain diameter are stable with minimal to no casing.
  - cnnsucks 9y ago
    Yes, geology is a big factor in engineering a well. Pressure is another. Every well is engineered to the prevailing conditions and requirements. Sometimes it is possible to elide heavy casing which can save large amounts of money.

abalone 9y ago

> geothermal checks all the boxes for renewables Article: "Although geothermal energy is still preferable to gas, coal and oil, it's not 'completely renewable and without problems... As soon as you start drilling you have issues to it, such as sulphur pollution and CO2 emission...'"

Beltiras 9y ago

Don't bill deep geothermal as any sort of green. There are usually emissions that have health consequences for the population around the power plant. The corrosion of the pipes bringing steam from the drill site to the turbines is massive. Drilling that deep and pumping water into the hole ups the risk of earthquakes. (source: I live in Reykjavík and have witnessed first-hand the increased stench from the Hellisheiði geothermal plant)

RealityVoid 9y ago
DISCLAIMER: I'm not an expert in this and I can be very off concerning this area. Having said this, I think the risk of man-made earthquakes is exaggerated. I mean, I think it might be possible to trigger small seismic events, but they should not be the destructive kind. I doubt we can trigger massive destructive eathquakes like this. Also, from what I understand, smaller seismic evnts should lower the energy that the bigger ones have.
- Beltiras 9y ago
  Tell that to the people of Selfoss and Hveragerði which have now become accustomed to smaller quakes on a more regular basis than usually in the past.
  - RealityVoid 9y ago
    Is it damaging though? That is the question I want answered. I mean, even in my post, I did not question the presence of more frequent small earthquakes, I questioned if these earthquakes are any sort of real issue that produces damages or simply unfounded panic.
    - Beltiras 9y ago
      Not being able to trust that the ground you stand on won't shake violently? Are you being serious?
      - 9y ago

fulafel 9y ago

Natural gas use will need to stop because of co2. IOW that "on par" cost of NG unsustainably excludes externalities.