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the earth receives the tiniest fraction of the sun's output. Space-based solar panels would have an almost unlimited amount of energy at their disposal...but ho

the earth receives the tiniest fraction of the sun's output. Space-based solar panels would have an almost unlimited amount of energy at their disposal...but how to get ithat energy down the well without James Bonds-ish laser beams?

eloff 4y ago
Space based solar is dumb. Let’s be generous and say you can get 2x output by having 24/7 sunlight, and that somehow we can beam it down efficiently enough that it’s a wash with gains from not having clouds or atmosphere in the way. Then the cost must be less than 2x for it to make sense over ground based solar. That’s just not realistic. Now when we have mining and manufacturing in space, and can use the energy there, that’s a different story.
- DennisP 4y ago
  A panel in geostationary gets five times as much energy as a panel on the ground. It's like noontime sun around the clock, plus none of the light is blocked in the atmosphere. And the biggest advantage isn't that 5X, it's eliminating the need for overcapacity and storage. https://illumin.usc.edu/space-based-solar-power-a-new-path-towards-sustainable-clean-energy/ https://illumin.usc.edu/space-based-solar-power-a-new-path-t...
  - Mistletoe 4y ago
    But isn't it infinitely cheaper and more efficient to just cover the earth with 5x as many panels? Losses in transmission from space would be significant (I'm seeing 9.6% microwave efficiency) and never mind that it costs $1000/kg to put something in space. https://en.wikipedia.org/wiki/Space-based_solar_power https://en.wikipedia.org/wiki/Space-based_solar_power
    - DennisP 4y ago
      Definitely wouldn't be feasible unless Starship works out at scale. If it does, launch costs go under $50/kg. Here is NASA's SPS-ALPHA study, which estimates 15 cents/kWh with $500/kg launch cost and minimal technological development (pdf): https://www.nasa.gov/sites/default/files/atoms/files/niac_2011_phasei_mankins_spsalpha_tagged.pdf https://www.nasa.gov/sites/default/files/atoms/files/niac_20...
  - eloff 4y ago
    That's just not going to happen. You could put 5x panels on the ground plus batteries and still have budget left over compared to launching it into orbit.
    - DennisP 4y ago
      That depends on launch costs and satellite design. The old designs from the 1970s would have been absurdly expensive. Modern designs like NASA's SPS-ALPHA are cheap to manufacture at scale. The book The Case for Space Solar Power has a detailed cost breakdown and puts a 2GW geostationary plant at 15 cents/kWh, but was published before SpaceX did much. I plugged in Starship launch costs and it came to 4 cents/kWh, which is pretty great for 24/7 clean power without storage. Here is NASA's study (pdf): https://www.nasa.gov/sites/default/files/atoms/files/niac_2011_phasei_mankins_spsalpha_tagged.pdf https://www.nasa.gov/sites/default/files/atoms/files/niac_20...
feet 4y ago
But why are lasers a bad option?
- orestarod 4y ago
  I guess because they can be used as weapons, if the said lasers can transfer enough energy with enough accuracy to cover real energy needs.
  - DennisP 4y ago
    Also because they get blocked by clouds. If you're not getting 24/7 power, you might as well put your solar panels on the ground.
LarryMullins 4y ago
Microwave power transmission seems like the obvious answer, but is fundamentally flawed due to the thinned-array curse: > It states that a transmitting antenna which is synthesized from a coherent phased array of smaller antenna apertures that are spaced apart will have a smaller minimum beam spot size, but the amount of power that is beamed into this main lobe is reduced by an exactly proportional amount, so that the total power density in the beam is constant. https://en.wikipedia.org/wiki/Thinned-array_curse https://en.wikipedia.org/wiki/Thinned-array_curse
- moloch-hai 4y ago
  People promoting space-based solar invariably pick Rube Goldberg complex designs that will reliably fail. A big, very low-mass reflector concentrating sunlight on laser tubes tuned for various wavelengths found in sunlight, and beaming visible light at only solar intensity onto wavelength-matched solar PV farms on the ground, at night, would substitute for storage. Since the light intensity is no more than in sunshine, there is no danger.

eloff 4y ago

Space based solar is dumb. Let’s be generous and say you can get 2x output by having 24/7 sunlight, and that somehow we can beam it down efficiently enough that it’s a wash with gains from not having clouds or atmosphere in the way. Then the cost must be less than 2x for it to make sense over ground based solar. That’s just not realistic. Now when we have mining and manufacturing in space, and can use the energy there, that’s a different story.

DennisP 4y ago
A panel in geostationary gets five times as much energy as a panel on the ground. It's like noontime sun around the clock, plus none of the light is blocked in the atmosphere. And the biggest advantage isn't that 5X, it's eliminating the need for overcapacity and storage. https://illumin.usc.edu/space-based-solar-power-a-new-path-towards-sustainable-clean-energy/ https://illumin.usc.edu/space-based-solar-power-a-new-path-t...
- Mistletoe 4y ago
  But isn't it infinitely cheaper and more efficient to just cover the earth with 5x as many panels? Losses in transmission from space would be significant (I'm seeing 9.6% microwave efficiency) and never mind that it costs $1000/kg to put something in space. https://en.wikipedia.org/wiki/Space-based_solar_power https://en.wikipedia.org/wiki/Space-based_solar_power
  - DennisP 4y ago
    Definitely wouldn't be feasible unless Starship works out at scale. If it does, launch costs go under $50/kg. Here is NASA's SPS-ALPHA study, which estimates 15 cents/kWh with $500/kg launch cost and minimal technological development (pdf): https://www.nasa.gov/sites/default/files/atoms/files/niac_2011_phasei_mankins_spsalpha_tagged.pdf https://www.nasa.gov/sites/default/files/atoms/files/niac_20...
- eloff 4y ago
  That's just not going to happen. You could put 5x panels on the ground plus batteries and still have budget left over compared to launching it into orbit.
  - DennisP 4y ago
    That depends on launch costs and satellite design. The old designs from the 1970s would have been absurdly expensive. Modern designs like NASA's SPS-ALPHA are cheap to manufacture at scale. The book The Case for Space Solar Power has a detailed cost breakdown and puts a 2GW geostationary plant at 15 cents/kWh, but was published before SpaceX did much. I plugged in Starship launch costs and it came to 4 cents/kWh, which is pretty great for 24/7 clean power without storage. Here is NASA's study (pdf): https://www.nasa.gov/sites/default/files/atoms/files/niac_2011_phasei_mankins_spsalpha_tagged.pdf https://www.nasa.gov/sites/default/files/atoms/files/niac_20...

feet 4y ago

But why are lasers a bad option?

orestarod 4y ago
I guess because they can be used as weapons, if the said lasers can transfer enough energy with enough accuracy to cover real energy needs.
- DennisP 4y ago
  Also because they get blocked by clouds. If you're not getting 24/7 power, you might as well put your solar panels on the ground.

LarryMullins 4y ago

Microwave power transmission seems like the obvious answer, but is fundamentally flawed due to the thinned-array curse: > It states that a transmitting antenna which is synthesized from a coherent phased array of smaller antenna apertures that are spaced apart will have a smaller minimum beam spot size, but the amount of power that is beamed into this main lobe is reduced by an exactly proportional amount, so that the total power density in the beam is constant. https://en.wikipedia.org/wiki/Thinned-array_curse https://en.wikipedia.org/wiki/Thinned-array_curse

moloch-hai 4y ago
People promoting space-based solar invariably pick Rube Goldberg complex designs that will reliably fail. A big, very low-mass reflector concentrating sunlight on laser tubes tuned for various wavelengths found in sunlight, and beaming visible light at only solar intensity onto wavelength-matched solar PV farms on the ground, at night, would substitute for storage. Since the light intensity is no more than in sunshine, there is no danger.