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Something I've always wondered. Wouldn't massive scale geothermal end up pumping more heat into the atmosphere that otherwise wouldn't be there? In contrast,

Something I've always wondered. Wouldn't massive scale geothermal end up pumping more heat into the atmosphere that otherwise wouldn't be there? In contrast, the energy collected by solar and wind generators is from the energy added to Earth by the sun and would be energy in our atmosphere regardless of whether or not we collect it. But it seems like the heat inside the Earth's core should be fairly well insulated by the lithosphere, and it only slowly leaks out over time. If we start pulling that energy out at a faster rate to generate electricity, could that have a noticeable net increase on total energy under the atmosphere, or is it such an insignificant amount of energy relative to the sun's to not even bother worrying about?

visarga 5y ago
How is that different from nuclear?
Uily 5y ago
Yes, but it will be orders of magnitude less than the sum total energy of solar energy across the total surface of the earth.
- eru 5y ago
  Similarly: Nuclear power plants, as nearly all power plants, work by heating water. That heat has to go somewhere eventually. But the amounts you'd need to make any difference to the atmosphere (compared to solar radiation) would be truly humongous.
  - anonporridge 5y ago
    I don't know if this would be any extra heat, because the radioactive material would already be decaying anyway if it was left in its natural state. Maybe the same problem where radioactive material would be left mostly underground and insulated where its heat would leak slowly. Then again, part of the Earth's core heat comes form radioactive decay. So in a way, geothermal is an indirect form of nuclear fission.
    - eru 5y ago
      Nuclear power plants don't just capture the energy from natural decay. Though the precise mechanism doesn't matter too much for my comment. Just assume I'm talking about fusion plants.
- anonporridge 5y ago
  Yeah. All civilization consumes around 17 TW of energy while the sun is constantly bombarding the Earth with 173,000 TW. We could rebase all of civilization on geothermal and the extra heat in the atmosphere would be a rounding error to the sun's energy.
  - pbhjpbhj 5y ago
    I don't think "it's a rounding error" is enough analysis here. A couple of meters of sea level rise, a couple of degrees temperature rise; these could be termed rounding errors.
    - Retric 5y ago
      Not degrees, thousandths of a degree, so possibly something like a centimeter if sea level rise. Considering nuclear and fossil fuels directly release stored energy and solar increase albido this isn’t a 1:1 increase in energy. Further the earth radiates more energy from hot places than cool, still you can approximate it as something like: Black body radiation is temperature in kelvin to the 4th power. (285 * (170,017^0.25 / 170,000^0.25) - 285) is an increase of ~0.007 C / (whatever our current percentage of energy from fossil fuels, nuclear, or solar).
    - anonporridge 5y ago
      It's far less than the variance of direct solar irradiation hitting the Earth given varying differences in distance from the sun in the Earth's orbit. https://en.wikipedia.org/wiki/Solar_constant#Solar_irradiance https://en.wikipedia.org/wiki/Solar_constant#Solar_irradianc... It looks like direct solar radiance is actually 173,000 TW plus or minus 6,000 TW.
  - onlyrealcuzzo 5y ago
    So if our energy consumption increases by 4% per year (current global average) for ~110 years, we'd need to capture / produce as much energy as the Sun hits us with. Crazy!
    - deleted 5y ago
hattmall 5y ago
That's a pretty solid question. I really don't know but hopefully someone else can answer. My guy hypothesis though is that even for all of our energy demands the amount pulled out would be pretty negligible. The reason being that only like 0.1% of the earth covered with solar panels would meet all our energy demands and heat wise geothermal should be much more efficient. The issue with heat and global warming isn't the actual heat it's the thicker atmosphere not letting it dissipate fast enough.
- erosenbe0 5y ago
  It's a non issue. But suppose you had a localized gigawatt leak into some wetlands. That would be trouble.
tinco 5y ago
You are correct in that the earth core is really well insulated from the surface. So well that the light of the sun delivers an order of magnitude more energy per M2 to the Earth's surface. That information also answers your question, our problem isn't with the amount heat we produce, it's with how much of that solar radiation we trap in our atmosphere due to the green house effect of CO2 and similar gases. So yeah we introduce a little bit more heat by drawing from the Earth's core, but it's nothing compared to what trapping the sun's energy with CO2 is doing to the planet right now. Conversely using that energy to remove CO2 from the atmosphere might even cool the planet, but that's a question for the next generation.
- anonporridge 5y ago
  I've had the thought for a while now that it might be a good idea to start changing the climate change narrative to a problem of planetary heat engineering, not simply a problem of GHG reduction. The current narrative is largely defeatist and regressive. It's largely about rolling back growth and the amount of energy civilization has harnessed. But if the narrative was altered to be a heat engineering problem, then it fundamentally changes how we think about it. Removing CO2 (insulation) is one option, but so are projects like solar reflection or some other forms of heat dissipation or heat sinking.
  - rland 5y ago
    I think there are other effects of increased CO2 concentration that are not well understood and could be catastrophic. Like ocean acidification. That actually scares me far more than the heat aspect.
    - anonporridge 5y ago
      I think we're deep into the territory of "literally anything we choose to do or not do is going to create a never ending game of whack-a-mole unintended consequences". We own the fate of our civilization and the environment it relies on. It's time to take ownership and stop cowering in the cave.
    - 5y ago
ComradePhil 5y ago
Solar is also trapping more energy than what would never be there. If the sun's rays just hit the ground, a portion of it would be reflected back. We're using dark material to aborb most of what would be reflected back and we end up trapping more energy than we should... Solar panels are around 15% efficient, which means 85% of this trapped energy is immediately converted to heat, heating the local environment... and the part which becomes electricity eventually gets converted to heat as well (no matter what you use it for). So, only ones I can think of which don't add additional heat to the planed may be wind and hydro.
- anonporridge 5y ago
  Good point. I wonder if solar energy is going to need to install high albedo surface area to offset it's low albedo energy absorption to satisfy some future version of ESG constraints.
- erosenbe0 5y ago
  Already been there done that. Asphalt roads and roofs do this en masse and create some slight overnight heat storage in urban environments. Solar is just a marginal addition I believe.
  - kragen 5y ago
    Also, much more importantly, oceans.
- tjoff 5y ago
  So 0% reflection?
- usrusr 5y ago
  If you've ever driven on a road approaching a hillside photovoltaics installation from the east at just the right time in the afternoon when it projects the sun right into traffic, you wouldn't be so sure to assume that 100% of incoming photons go either to electricity or to heat... but yeah, high albedo photovoltaic might be an interesting research topic. We have semi-translucent panels that seem to only sacrifice so much efficiency, some room for high albedo should exist (probably not much). Market would of course be people showing off that they can afford different looks, like those musk-shingles. But efficiency also dereases with temperature, so perhaps this might be another angle ? Invoking the impact on total earth albedo certainly won't drive any buying decisions, tragedy of the commons and all that...
jillesvangurp 5y ago
It's not significant indeed. Imagine a balloon the size of the earth and pricking a tiny hole in it. Does it 1) rapidly deflate, or 2) does not change measurably in size at all for millions/billions of years? Replace your mental model of a balloon with that of a massive amount of hot stuff surrounded by a thin crust and you have your answer. Geothermal works pretty well anywhere from a technical point of view. The main issue is that drilling holes is expensive. There is a company called Eavor that is actually re-purposing former (failed) oil drilling attempts to get a head start on that. That is smart. Even so, they are on the expensive side of the spectrum. It's just a lot of capital expenses to get to warm enough temperatures that you can get steam to drive a turbine. And of course you need either a lot of holes or a very big one to scale it. Eavor claims that they are going to be essential for baseload. IMHO they might be too expensive for that but we'll see if they can lower their cost over time.
Archelaos 5y ago
The heat is not the problem. It radiates into space quite quickly. The current world energy supply per year is over 160 TWh.[1] By comparison, the erruption of Mount Tambora in 1815 released aprox. 237.5 times more energy in a single incident (~38 PWh).[2] The problem at that time was not an extended (regional) heat wave, but the substances that entered the atmosphere and remained there for several years, causing a global weather change. [1] https://en.wikipedia.org/wiki/World_energy_supply_and_consumption#Total_Energy_Supply https://en.wikipedia.org/wiki/World_energy_supply_and_consum... [2] Other less spectacular examples: 160 TWh is equivalent of 5 to 6 times the energy released by the Mt. St. Helens erruption of 1980 (~28 TWh) or the 2004 Indian Ocean earthquake (~30.6 TWh), or half of the energy released by the 1883 eruption of Krakatoa (~232 TWh), or 1/4 of all nuclear bomb explosions so far (628 TWh). For this an other examples see: https://en.wikipedia.org/wiki/TNT_equivalent https://en.wikipedia.org/wiki/TNT_equivalent
kragen 5y ago
It could. The available fossil sensible heat energy is something like hundreds of millions of years of sunlight. Right now geothermal is uneconomic except in special situations, and human world marketed energy consumption is four orders of magnitude smaller than insolation, so it’s not yet a practical concern.
- kragen 5y ago
  It turns out to be millions of years of sunlight, not hundreds of millions. You have: earthmass 2000 K 1J/g/K You want: J * 1.1944337e+31 / 8.3721685e-32 You have: earthmass 2000 K 1J/g/K/(circlearea (earthradius) 1000 W/m2) You want: years * 2968252.9 / 3.3689851e-07
dan_mctree 5y ago
The amount of heat in the atmosphere at any point doesn't really matter all that much for global warming. What matters is the break-even point between the amount of energy we gain from and lose to space. Since the earth emits more energy if it's warmer (black body radiation), the break-even point relates to the temperature of the earth. If we change something about the earth's in or output of energy, the earth's temperature will naturally rise until the break even point is reached again. By introducing greenhouse gasses, we are affecting earth's ability to radiate energy to space and thus the temperature at which we have our break-even point. Should all greenhouse gasses disappear, the earth would rapidly start cooling until it reaches its new break-even point.
- gmuslera 5y ago
  We aren't talking about a system with an evenly distributed energy. It wouldn't be life on Earth if the global temperature average was between what is now the temperature of the atmosphere, and all the ones below surface. As long as the thermal isolation remains in place it shouldn't be a problem and the biggest foe should be the unbalance between heat in and heat out from sun/space, but what if we do a big scale and sustained thermal transfer between the core and the surface? I know, I'm oversimplifying a lot, and the orders of what humans can do may be dwarfed by any volcanic eruption, but it should be a safe margin at some point at which the scale and time of heat transfer with underground may start to affect global average temperature.

visarga 5y ago

How is that different from nuclear?

Uily 5y ago

Yes, but it will be orders of magnitude less than the sum total energy of solar energy across the total surface of the earth.

eru 5y ago
Similarly: Nuclear power plants, as nearly all power plants, work by heating water. That heat has to go somewhere eventually. But the amounts you'd need to make any difference to the atmosphere (compared to solar radiation) would be truly humongous.
- anonporridge 5y ago
  I don't know if this would be any extra heat, because the radioactive material would already be decaying anyway if it was left in its natural state. Maybe the same problem where radioactive material would be left mostly underground and insulated where its heat would leak slowly. Then again, part of the Earth's core heat comes form radioactive decay. So in a way, geothermal is an indirect form of nuclear fission.
  - eru 5y ago
    Nuclear power plants don't just capture the energy from natural decay. Though the precise mechanism doesn't matter too much for my comment. Just assume I'm talking about fusion plants.
anonporridge 5y ago
Yeah. All civilization consumes around 17 TW of energy while the sun is constantly bombarding the Earth with 173,000 TW. We could rebase all of civilization on geothermal and the extra heat in the atmosphere would be a rounding error to the sun's energy.
- pbhjpbhj 5y ago
  I don't think "it's a rounding error" is enough analysis here. A couple of meters of sea level rise, a couple of degrees temperature rise; these could be termed rounding errors.
  - Retric 5y ago
    Not degrees, thousandths of a degree, so possibly something like a centimeter if sea level rise. Considering nuclear and fossil fuels directly release stored energy and solar increase albido this isn’t a 1:1 increase in energy. Further the earth radiates more energy from hot places than cool, still you can approximate it as something like: Black body radiation is temperature in kelvin to the 4th power. (285 * (170,017^0.25 / 170,000^0.25) - 285) is an increase of ~0.007 C / (whatever our current percentage of energy from fossil fuels, nuclear, or solar).
  - anonporridge 5y ago
    It's far less than the variance of direct solar irradiation hitting the Earth given varying differences in distance from the sun in the Earth's orbit. https://en.wikipedia.org/wiki/Solar_constant#Solar_irradiance https://en.wikipedia.org/wiki/Solar_constant#Solar_irradianc... It looks like direct solar radiance is actually 173,000 TW plus or minus 6,000 TW.
- onlyrealcuzzo 5y ago
  So if our energy consumption increases by 4% per year (current global average) for ~110 years, we'd need to capture / produce as much energy as the Sun hits us with. Crazy!
  - deleted 5y ago

hattmall 5y ago

That's a pretty solid question. I really don't know but hopefully someone else can answer. My guy hypothesis though is that even for all of our energy demands the amount pulled out would be pretty negligible. The reason being that only like 0.1% of the earth covered with solar panels would meet all our energy demands and heat wise geothermal should be much more efficient. The issue with heat and global warming isn't the actual heat it's the thicker atmosphere not letting it dissipate fast enough.

erosenbe0 5y ago
It's a non issue. But suppose you had a localized gigawatt leak into some wetlands. That would be trouble.

tinco 5y ago

You are correct in that the earth core is really well insulated from the surface. So well that the light of the sun delivers an order of magnitude more energy per M2 to the Earth's surface. That information also answers your question, our problem isn't with the amount heat we produce, it's with how much of that solar radiation we trap in our atmosphere due to the green house effect of CO2 and similar gases. So yeah we introduce a little bit more heat by drawing from the Earth's core, but it's nothing compared to what trapping the sun's energy with CO2 is doing to the planet right now. Conversely using that energy to remove CO2 from the atmosphere might even cool the planet, but that's a question for the next generation.

anonporridge 5y ago
I've had the thought for a while now that it might be a good idea to start changing the climate change narrative to a problem of planetary heat engineering, not simply a problem of GHG reduction. The current narrative is largely defeatist and regressive. It's largely about rolling back growth and the amount of energy civilization has harnessed. But if the narrative was altered to be a heat engineering problem, then it fundamentally changes how we think about it. Removing CO2 (insulation) is one option, but so are projects like solar reflection or some other forms of heat dissipation or heat sinking.
- rland 5y ago
  I think there are other effects of increased CO2 concentration that are not well understood and could be catastrophic. Like ocean acidification. That actually scares me far more than the heat aspect.
  - anonporridge 5y ago
    I think we're deep into the territory of "literally anything we choose to do or not do is going to create a never ending game of whack-a-mole unintended consequences". We own the fate of our civilization and the environment it relies on. It's time to take ownership and stop cowering in the cave.
  - 5y ago

ComradePhil 5y ago

Solar is also trapping more energy than what would never be there. If the sun's rays just hit the ground, a portion of it would be reflected back. We're using dark material to aborb most of what would be reflected back and we end up trapping more energy than we should... Solar panels are around 15% efficient, which means 85% of this trapped energy is immediately converted to heat, heating the local environment... and the part which becomes electricity eventually gets converted to heat as well (no matter what you use it for). So, only ones I can think of which don't add additional heat to the planed may be wind and hydro.

anonporridge 5y ago
Good point. I wonder if solar energy is going to need to install high albedo surface area to offset it's low albedo energy absorption to satisfy some future version of ESG constraints.
erosenbe0 5y ago
Already been there done that. Asphalt roads and roofs do this en masse and create some slight overnight heat storage in urban environments. Solar is just a marginal addition I believe.
- kragen 5y ago
  Also, much more importantly, oceans.
tjoff 5y ago
So 0% reflection?
usrusr 5y ago
If you've ever driven on a road approaching a hillside photovoltaics installation from the east at just the right time in the afternoon when it projects the sun right into traffic, you wouldn't be so sure to assume that 100% of incoming photons go either to electricity or to heat... but yeah, high albedo photovoltaic might be an interesting research topic. We have semi-translucent panels that seem to only sacrifice so much efficiency, some room for high albedo should exist (probably not much). Market would of course be people showing off that they can afford different looks, like those musk-shingles. But efficiency also dereases with temperature, so perhaps this might be another angle ? Invoking the impact on total earth albedo certainly won't drive any buying decisions, tragedy of the commons and all that...

jillesvangurp 5y ago

It's not significant indeed. Imagine a balloon the size of the earth and pricking a tiny hole in it. Does it 1) rapidly deflate, or 2) does not change measurably in size at all for millions/billions of years? Replace your mental model of a balloon with that of a massive amount of hot stuff surrounded by a thin crust and you have your answer. Geothermal works pretty well anywhere from a technical point of view. The main issue is that drilling holes is expensive. There is a company called Eavor that is actually re-purposing former (failed) oil drilling attempts to get a head start on that. That is smart. Even so, they are on the expensive side of the spectrum. It's just a lot of capital expenses to get to warm enough temperatures that you can get steam to drive a turbine. And of course you need either a lot of holes or a very big one to scale it. Eavor claims that they are going to be essential for baseload. IMHO they might be too expensive for that but we'll see if they can lower their cost over time.

Archelaos 5y ago

The heat is not the problem. It radiates into space quite quickly. The current world energy supply per year is over 160 TWh.[1] By comparison, the erruption of Mount Tambora in 1815 released aprox. 237.5 times more energy in a single incident (~38 PWh).[2] The problem at that time was not an extended (regional) heat wave, but the substances that entered the atmosphere and remained there for several years, causing a global weather change. [1] https://en.wikipedia.org/wiki/World_energy_supply_and_consumption#Total_Energy_Supply https://en.wikipedia.org/wiki/World_energy_supply_and_consum... [2] Other less spectacular examples: 160 TWh is equivalent of 5 to 6 times the energy released by the Mt. St. Helens erruption of 1980 (~28 TWh) or the 2004 Indian Ocean earthquake (~30.6 TWh), or half of the energy released by the 1883 eruption of Krakatoa (~232 TWh), or 1/4 of all nuclear bomb explosions so far (628 TWh). For this an other examples see: https://en.wikipedia.org/wiki/TNT_equivalent https://en.wikipedia.org/wiki/TNT_equivalent

kragen 5y ago

It could. The available fossil sensible heat energy is something like hundreds of millions of years of sunlight. Right now geothermal is uneconomic except in special situations, and human world marketed energy consumption is four orders of magnitude smaller than insolation, so it’s not yet a practical concern.

kragen 5y ago
It turns out to be millions of years of sunlight, not hundreds of millions. You have: earthmass 2000 K 1J/g/K You want: J * 1.1944337e+31 / 8.3721685e-32 You have: earthmass 2000 K 1J/g/K/(circlearea (earthradius) 1000 W/m2) You want: years * 2968252.9 / 3.3689851e-07

dan_mctree 5y ago

The amount of heat in the atmosphere at any point doesn't really matter all that much for global warming. What matters is the break-even point between the amount of energy we gain from and lose to space. Since the earth emits more energy if it's warmer (black body radiation), the break-even point relates to the temperature of the earth. If we change something about the earth's in or output of energy, the earth's temperature will naturally rise until the break even point is reached again. By introducing greenhouse gasses, we are affecting earth's ability to radiate energy to space and thus the temperature at which we have our break-even point. Should all greenhouse gasses disappear, the earth would rapidly start cooling until it reaches its new break-even point.

gmuslera 5y ago
We aren't talking about a system with an evenly distributed energy. It wouldn't be life on Earth if the global temperature average was between what is now the temperature of the atmosphere, and all the ones below surface. As long as the thermal isolation remains in place it shouldn't be a problem and the biggest foe should be the unbalance between heat in and heat out from sun/space, but what if we do a big scale and sustained thermal transfer between the core and the surface? I know, I'm oversimplifying a lot, and the orders of what humans can do may be dwarfed by any volcanic eruption, but it should be a safe margin at some point at which the scale and time of heat transfer with underground may start to affect global average temperature.