6 ms·

The detail that has stuck in my mind since the last time I read about this is: Thermodynamically speaking, if you transmit electricity from outside the Earth o

by rsync 2y ago

The detail that has stuck in my mind since the last time I read about this is: Thermodynamically speaking, if you transmit electricity from outside the Earth onto the Earth – even if you do it perfectly efficiently – you are, by definition, heating the planet. Based on that I concluded that it is superior to generate electricity with inputs that are already hitting the Earth… But I’d be very interested to learn more about this.

tectonic 2y ago
This is false, if your SBSP conversion efficiency on the ground is better than solar panels on the ground then you will add less energy to earth by collecting the power in space and transmitting it to the ground then by changing the reflective albedo of desert to a very nonreflective material like solar panels.
- pfdietz 2y ago
  Hmm. If your PV has efficiency > the albedo of the ground it covers, it will be better than SBSP, even if the rectenna is 100% efficient (assuming the emissivity of the PV is at least as good as that of the desert in the far IR). This assumes the rectenna has the same optical properties as the ground it covers. One could improve the PV by making it highly reflective in the near IR at wavelengths below the bandgap of the cells, while still being highly emissive at the longer wavelengths where it will radiate heat.
bee_rider 2y ago
You could put the solar panels between the sun and Earth so they only capture photon that would have otherwise hit Earth, if that really matters. This would even be nice because if we wanted to cool the planet down we could just redirect some rays. But I think using an appreciable amount of the power provided to Earth by the sun is still sci-fi stuff anyway, so we probably can’t make an appreciable dent either way. Sagan put us at around Kardashev .7, it is a log scale shifted by a constant, apparently we’re under .2%, of what hits the Earth, I guess. https://en.m.wikipedia.org/wiki/Kardashev_scale https://en.m.wikipedia.org/wiki/Kardashev_scale
- jandrese 2y ago
  If you set the thing up in the L1 Lagrange point it will have the same day/night problem that traditional solar has. You would need at least two, but probably realistically 3 different antenna farms to collect the power and the satellite would need to be able to track the beam across the surface of the Earth. Most of the proposals I've seen have the array in geosynchronous orbit so it can easily remain pointed at a fixed spot on the Earth.
  - Retric 2y ago
    You could also beam power from L1 to geosynchronous orbit and then to a single ground station. It really depends on how efficiently you can beam power, but hitting Type 1 on the Kardashev scale hits limitations based on radiative cooling into space vs incoming energy. However, it makes sense to have hundreds of ground stations simply to minimize transmission losses on the ground. And presumably utilizing ground stations 24/7 is vastly less critical than maximizing the return on space based infrastructure.
    - RF_Savage 2y ago
      At these power levels the power beaming array starts to look a lot like a weapon. One with a beam that can target distinct areas. Easy way to fry large amounts of your adversarys telecoms infra. It will not put you back to the stone age, but 1970-1980 is not out of the question. For wireless communications that is.
  - pfdietz 2y ago
    One could put SBSP at the Earth-Sun L2 point, and just use ground based solar during the day. Weirdly, this would mean in winter at high latitudes one would mostly be getting solar power at night! At the distance of the L2 point laser power beaming would probably be necessary to keep the transmitter and receiver sufficiently small.
gmuslera 2y ago
Not all that energy will end as heat. And the surface that it may cover won't be significant compared with the Earth one. And if it is, it may shadow enough surface to actually cool down Earth. In any case, it won't be worse than releasing a good amount of the captured solar energy in chemical form for millions of years in around a century.
glitchc 2y ago
I think the more important facet is the output stage. Almost all energy consumed gets converted to heat, with only a small portion doing usable work. Unless there's a massive improvement in the electrical foundations of compute, we will be producing large amounts of heat no matter where the energy is sourced from.
- beefield 2y ago
  unless... the compute happens also in space? Given how dirt cheap solar has become, how cheap shipping stuff to space is becoming and how little there are clouds and nights in the space making solar power production intermittent, it sounds like it might be economically feasible in not so distant future. (no, I haven't done any math on this. If it checks out, feel free to steal the idea)
  - rockemsockem 2y ago
    Heat dissipation in space is hard.
    - ben_w 2y ago
      And the Earth is in space, so if we get to the power consumption level where Earth governments need to care about the direct planetary heating effect of the energy source, it's still a win to do the hard thing (dissipation) somewhere else, like the Moon or something.
  - exe34 2y ago
    Ugh solar wind and cosmic rays. You'd need to use very inefficient CPUs with enormous features instead of the latest small node.
    - rockemsockem 2y ago
      Also true!!
    - actionfromafar 2y ago
epistasis 2y ago
The same thing happens when we create heat on earth with nuclear energy, when >50% is directly used to heat the earth via waste heat, and the electrical part becomes >99% waste heat (some tiny fraction of energy is probably permanently converted to chemical bonds, etc.) However, this is completely dwarfed by the dynamics of flux in and out of the earth. I forget the exact order of magnitude but I think it's around 100TW, and of course about that amount needs to be rejected to space. The key dynamics that provide us balance are of course the exact and precise quantities of greenhouse gases in the atmosphere, albedo, etc. And of course, coal and natural gas are releasing stored heat energy too, but their contributions to changes in the atmosphere far exceed the contribution from direct heat energy on the surface of the earth.
- maxerickson 2y ago
  The flux is roughly (but more than) 100 petawatts. Human energy utilization is on the order of 100 terawatts.
  - fastball 2y ago
    Really? So we're only 3 orders of magnitude off? Seems like we can definitely get to appreciable levels of i/o in the near future.
    - nojvek 2y ago
      Total solar energy hitting earth = ~45 Petawatts Total power used by humans = 16 Terawatts. https://www.nasa.gov/wp-content/uploads/2015/03/135642main_balance_trifold21.pdf https://www.nasa.gov/wp-content/uploads/2015/03/135642main_b... What we get from the Sun in one hour, is how much we use for the whole year. All our energy needs can be covered if we can tap into just 0.00001% of energy received. About 100km2 worth of solar panels. If every residential and commercial building was covered with solar roof - we’d have all our energy needs covered during day time. It’s free energy if we know how to use it. Plants do and they make up >99.9% of biomass on this planet. The problem with C02 is it traps the heat. All useful work is done when high energy packets from sun in ultraviolet and visible light get dissipated into heat (infrared). If we don’t solve greenhouse gas problem, we can’t use more energy since we’d be out of equilibrium.
IshKebab 2y ago
This is like the very last possible issue with this plan. It's like worrying about a space elevator unbalancing the earth's rotation. You need to get a better handle on orders of magnitude.
- mitthrowaway2 2y ago
  Exponential growth sneaks up on you. They probably thought the same thing in 1895 about the negligible magnitude of human greenhouse gas emissions.
  - deleted 2y ago
    [deleted]
  - mjhay 2y ago
    There's no exponential growth, that's thermodynamically impossible. Heating the Earth with the microwaves would increase the Earth's radiation into space commensurately. It doesn't get stored forever. This would result in a new equilibrium almost immediately, with an unmeasurably greater temperature. The Earth is always almost exactly in a radiative balance with space, except on pretty short timescales. If it weren't, we'd quickly cook. The radiation the Earth receives from the Sun fluctuates orders of magnitude more over solar cycles, but it's debated whether that even has a meaningful effect on global temperature.
    - mitthrowaway2 2y ago
      (I'm not referring to exponential growth in temperature over time due to constant input power, but rather to exponential growth in input power over time because it's required for economic growth).
      - pdonis 2y ago
        > exponential growth in input power over time because it's required for economic growth It isn't. The amount of energy (and raw materials generally) required to produce a given amount of economic output is not constant. It gets smaller as technology advances. That offsets the effect of increased economic output. Indeed, as more and more economic output becomes information instead of physical objects, the average amount of energy required per unit of economic output will shrink even more.
m463 2y ago
miniscule in comparison to greenhouse gas emissions, which can make the entire planet capture and hold more energy, not just a satellite.
deleted 2y ago
[deleted]
TheDudeMan 2y ago
All nuclear power is also extra heat for the earth.
- pfdietz 2y ago
  And much more, per unit of electricity consumed.
kadoban 2y ago
This is orders of magnitude away from being anything like a concern.
- tehjoker 2y ago
  If you read some criticisms of our economic system, they propose that growth will continue unabated without any limits, but after a couple hundred years, that exponential gets to the point that all the waste heat cannot be dissipated from the earth any longer and it all breaks down.
  - deleted 2y ago
    [deleted]
  - rgmerk 2y ago
    If you’re postulating unbounded growth, seems pretty arbitrary to not postulate engineering solutions to this problem (eg shift the energy intensive industry off-Earth).
mjhay 2y ago
The Earth is in radiative balance with space on all but very short timescales. The extra heat, even if it were enough to matter, dissipates quickly.
- schiffern 2y ago
  We're not talking about just a one-time pulse of heat, it would be a constant stream of energy. To maintain the same radiant balance the Earth's surface would need to reach a higher equilibrium temperature. We currently have an energy budget that's 0.1% of insolation (and compounding growth at 2-5% per year), so if SBSP actually scales to its market opportunity then the effect could certainly be large enough to matter.
thelastgallon 2y ago
67% of energy is wasted as heat: https://flowcharts.llnl.gov/sites/flowcharts/files/2023-10/US%20Energy%202022.png https://flowcharts.llnl.gov/sites/flowcharts/files/2023-10/U... This will change when we switch to renewables.
- Turing_Machine 2y ago
  What? Renewables are still subject to the laws of thermodynamics and other laws of physics. https://en.wikipedia.org/wiki/Heat_engine#Efficiency https://en.wikipedia.org/wiki/Heat_engine#Efficiency Typical power stations (whether fueld by renewables or not) have efficiencies considerably less than 50% (the examples in this article give 40% efficiency for coal, 48% for nuclear, and 33% for geothermal). Photovoltaics (not being Carnot-cycle heat engines) aren't subject to these specific limitations, but they have their own problems. Typical efficiencies for current mass-production models are around 20%, while "lab curiosity"-level cells still haven't broken 50%. Note that this is just the generating side. There are also similar waste heat losses on the consumption side (for example, charging and discharging batteries is anything but 100% efficient, as anyone who's actually tried to use a modern laptop on his lap can attest).
  - schiffern 2y ago
    >Photovoltaics... are around 20% The difference is, that 80% doesn't show up on anyone's "books." For coal, you actually need to go dig that 60% out of the ground and burn it, and it still emits a bunch of CO2. For a fuller articulation of the point HN user thelastgallon is making, see this link: https://www.sustainabilitybynumbers.com/p/electrification-energy-efficiency https://www.sustainabilitybynumbers.com/p/electrification-en...
    - Turing_Machine 2y ago
      > The difference is, that 80% doesn't show up on anyone's "books." Well, no. You still have to pay the amortized cost of the installation and real estate, the salaries of the employees, and many other things, all of which would be less if the efficiency were higher than 20%. For example, if the photovoltaics were 40% efficient (the same as coal), you'd need only half the real estate, half the semiconductor-grade silicon, and likely half the cost of many maintenance activities, none of which are free. > https://www.sustainabilitybynumbers.com/p/electrification-en https://www.sustainabilitybynumbers.com/p/electrification-en... This site doesn't even mention solar or the efficiency thereof.
creer 2y ago
You also affect how much energy (heat) you radiate from earth's surface into space, by choosing the right color, materials of buildings or land around you.
deleted 2y ago
[deleted]

by rsync 2y ago

tectonic 2y ago

This is false, if your SBSP conversion efficiency on the ground is better than solar panels on the ground then you will add less energy to earth by collecting the power in space and transmitting it to the ground then by changing the reflective albedo of desert to a very nonreflective material like solar panels.

pfdietz 2y ago
Hmm. If your PV has efficiency > the albedo of the ground it covers, it will be better than SBSP, even if the rectenna is 100% efficient (assuming the emissivity of the PV is at least as good as that of the desert in the far IR). This assumes the rectenna has the same optical properties as the ground it covers. One could improve the PV by making it highly reflective in the near IR at wavelengths below the bandgap of the cells, while still being highly emissive at the longer wavelengths where it will radiate heat.

bee_rider 2y ago

You could put the solar panels between the sun and Earth so they only capture photon that would have otherwise hit Earth, if that really matters. This would even be nice because if we wanted to cool the planet down we could just redirect some rays. But I think using an appreciable amount of the power provided to Earth by the sun is still sci-fi stuff anyway, so we probably can’t make an appreciable dent either way. Sagan put us at around Kardashev .7, it is a log scale shifted by a constant, apparently we’re under .2%, of what hits the Earth, I guess. https://en.m.wikipedia.org/wiki/Kardashev_scale https://en.m.wikipedia.org/wiki/Kardashev_scale

jandrese 2y ago
If you set the thing up in the L1 Lagrange point it will have the same day/night problem that traditional solar has. You would need at least two, but probably realistically 3 different antenna farms to collect the power and the satellite would need to be able to track the beam across the surface of the Earth. Most of the proposals I've seen have the array in geosynchronous orbit so it can easily remain pointed at a fixed spot on the Earth.
- Retric 2y ago
  You could also beam power from L1 to geosynchronous orbit and then to a single ground station. It really depends on how efficiently you can beam power, but hitting Type 1 on the Kardashev scale hits limitations based on radiative cooling into space vs incoming energy. However, it makes sense to have hundreds of ground stations simply to minimize transmission losses on the ground. And presumably utilizing ground stations 24/7 is vastly less critical than maximizing the return on space based infrastructure.
  - RF_Savage 2y ago
    At these power levels the power beaming array starts to look a lot like a weapon. One with a beam that can target distinct areas. Easy way to fry large amounts of your adversarys telecoms infra. It will not put you back to the stone age, but 1970-1980 is not out of the question. For wireless communications that is.
- pfdietz 2y ago
  One could put SBSP at the Earth-Sun L2 point, and just use ground based solar during the day. Weirdly, this would mean in winter at high latitudes one would mostly be getting solar power at night! At the distance of the L2 point laser power beaming would probably be necessary to keep the transmitter and receiver sufficiently small.

gmuslera 2y ago

Not all that energy will end as heat. And the surface that it may cover won't be significant compared with the Earth one. And if it is, it may shadow enough surface to actually cool down Earth. In any case, it won't be worse than releasing a good amount of the captured solar energy in chemical form for millions of years in around a century.

glitchc 2y ago

I think the more important facet is the output stage. Almost all energy consumed gets converted to heat, with only a small portion doing usable work. Unless there's a massive improvement in the electrical foundations of compute, we will be producing large amounts of heat no matter where the energy is sourced from.

beefield 2y ago
unless... the compute happens also in space? Given how dirt cheap solar has become, how cheap shipping stuff to space is becoming and how little there are clouds and nights in the space making solar power production intermittent, it sounds like it might be economically feasible in not so distant future. (no, I haven't done any math on this. If it checks out, feel free to steal the idea)
- rockemsockem 2y ago
  Heat dissipation in space is hard.
  - ben_w 2y ago
    And the Earth is in space, so if we get to the power consumption level where Earth governments need to care about the direct planetary heating effect of the energy source, it's still a win to do the hard thing (dissipation) somewhere else, like the Moon or something.
- exe34 2y ago
  Ugh solar wind and cosmic rays. You'd need to use very inefficient CPUs with enormous features instead of the latest small node.
  - rockemsockem 2y ago
    Also true!!
  - actionfromafar 2y ago

epistasis 2y ago

The same thing happens when we create heat on earth with nuclear energy, when >50% is directly used to heat the earth via waste heat, and the electrical part becomes >99% waste heat (some tiny fraction of energy is probably permanently converted to chemical bonds, etc.) However, this is completely dwarfed by the dynamics of flux in and out of the earth. I forget the exact order of magnitude but I think it's around 100TW, and of course about that amount needs to be rejected to space. The key dynamics that provide us balance are of course the exact and precise quantities of greenhouse gases in the atmosphere, albedo, etc. And of course, coal and natural gas are releasing stored heat energy too, but their contributions to changes in the atmosphere far exceed the contribution from direct heat energy on the surface of the earth.

maxerickson 2y ago
The flux is roughly (but more than) 100 petawatts. Human energy utilization is on the order of 100 terawatts.
- fastball 2y ago
  Really? So we're only 3 orders of magnitude off? Seems like we can definitely get to appreciable levels of i/o in the near future.
  - nojvek 2y ago
    Total solar energy hitting earth = ~45 Petawatts Total power used by humans = 16 Terawatts. https://www.nasa.gov/wp-content/uploads/2015/03/135642main_balance_trifold21.pdf https://www.nasa.gov/wp-content/uploads/2015/03/135642main_b... What we get from the Sun in one hour, is how much we use for the whole year. All our energy needs can be covered if we can tap into just 0.00001% of energy received. About 100km2 worth of solar panels. If every residential and commercial building was covered with solar roof - we’d have all our energy needs covered during day time. It’s free energy if we know how to use it. Plants do and they make up >99.9% of biomass on this planet. The problem with C02 is it traps the heat. All useful work is done when high energy packets from sun in ultraviolet and visible light get dissipated into heat (infrared). If we don’t solve greenhouse gas problem, we can’t use more energy since we’d be out of equilibrium.

IshKebab 2y ago

This is like the very last possible issue with this plan. It's like worrying about a space elevator unbalancing the earth's rotation. You need to get a better handle on orders of magnitude.

mitthrowaway2 2y ago
Exponential growth sneaks up on you. They probably thought the same thing in 1895 about the negligible magnitude of human greenhouse gas emissions.
- deleted 2y ago
  [deleted]
- mjhay 2y ago
  There's no exponential growth, that's thermodynamically impossible. Heating the Earth with the microwaves would increase the Earth's radiation into space commensurately. It doesn't get stored forever. This would result in a new equilibrium almost immediately, with an unmeasurably greater temperature. The Earth is always almost exactly in a radiative balance with space, except on pretty short timescales. If it weren't, we'd quickly cook. The radiation the Earth receives from the Sun fluctuates orders of magnitude more over solar cycles, but it's debated whether that even has a meaningful effect on global temperature.
  - mitthrowaway2 2y ago
    (I'm not referring to exponential growth in temperature over time due to constant input power, but rather to exponential growth in input power over time because it's required for economic growth).
    - pdonis 2y ago
      > exponential growth in input power over time because it's required for economic growth It isn't. The amount of energy (and raw materials generally) required to produce a given amount of economic output is not constant. It gets smaller as technology advances. That offsets the effect of increased economic output. Indeed, as more and more economic output becomes information instead of physical objects, the average amount of energy required per unit of economic output will shrink even more.

m463 2y ago

miniscule in comparison to greenhouse gas emissions, which can make the entire planet capture and hold more energy, not just a satellite.

deleted 2y ago

[deleted]

TheDudeMan 2y ago

All nuclear power is also extra heat for the earth.

pfdietz 2y ago
And much more, per unit of electricity consumed.

kadoban 2y ago

This is orders of magnitude away from being anything like a concern.

tehjoker 2y ago
If you read some criticisms of our economic system, they propose that growth will continue unabated without any limits, but after a couple hundred years, that exponential gets to the point that all the waste heat cannot be dissipated from the earth any longer and it all breaks down.
- deleted 2y ago
  [deleted]
- rgmerk 2y ago
  If you’re postulating unbounded growth, seems pretty arbitrary to not postulate engineering solutions to this problem (eg shift the energy intensive industry off-Earth).

mjhay 2y ago

The Earth is in radiative balance with space on all but very short timescales. The extra heat, even if it were enough to matter, dissipates quickly.

schiffern 2y ago
We're not talking about just a one-time pulse of heat, it would be a constant stream of energy. To maintain the same radiant balance the Earth's surface would need to reach a higher equilibrium temperature. We currently have an energy budget that's 0.1% of insolation (and compounding growth at 2-5% per year), so if SBSP actually scales to its market opportunity then the effect could certainly be large enough to matter.

thelastgallon 2y ago

67% of energy is wasted as heat: https://flowcharts.llnl.gov/sites/flowcharts/files/2023-10/US%20Energy%202022.png https://flowcharts.llnl.gov/sites/flowcharts/files/2023-10/U... This will change when we switch to renewables.

Turing_Machine 2y ago
What? Renewables are still subject to the laws of thermodynamics and other laws of physics. https://en.wikipedia.org/wiki/Heat_engine#Efficiency https://en.wikipedia.org/wiki/Heat_engine#Efficiency Typical power stations (whether fueld by renewables or not) have efficiencies considerably less than 50% (the examples in this article give 40% efficiency for coal, 48% for nuclear, and 33% for geothermal). Photovoltaics (not being Carnot-cycle heat engines) aren't subject to these specific limitations, but they have their own problems. Typical efficiencies for current mass-production models are around 20%, while "lab curiosity"-level cells still haven't broken 50%. Note that this is just the generating side. There are also similar waste heat losses on the consumption side (for example, charging and discharging batteries is anything but 100% efficient, as anyone who's actually tried to use a modern laptop on his lap can attest).
- schiffern 2y ago
  >Photovoltaics... are around 20% The difference is, that 80% doesn't show up on anyone's "books." For coal, you actually need to go dig that 60% out of the ground and burn it, and it still emits a bunch of CO2. For a fuller articulation of the point HN user thelastgallon is making, see this link: https://www.sustainabilitybynumbers.com/p/electrification-energy-efficiency https://www.sustainabilitybynumbers.com/p/electrification-en...
  - Turing_Machine 2y ago
    > The difference is, that 80% doesn't show up on anyone's "books." Well, no. You still have to pay the amortized cost of the installation and real estate, the salaries of the employees, and many other things, all of which would be less if the efficiency were higher than 20%. For example, if the photovoltaics were 40% efficient (the same as coal), you'd need only half the real estate, half the semiconductor-grade silicon, and likely half the cost of many maintenance activities, none of which are free. > https://www.sustainabilitybynumbers.com/p/electrification-en https://www.sustainabilitybynumbers.com/p/electrification-en... This site doesn't even mention solar or the efficiency thereof.

creer 2y ago

You also affect how much energy (heat) you radiate from earth's surface into space, by choosing the right color, materials of buildings or land around you.

deleted 2y ago

[deleted]